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THE 



GEOLOGY 

OF 

PENNSYLVAN 

1) 



A GOVERNMENT SURVEY 



BY 



HENRY DARWIN ROGERS 

STATE GEOLOGIST 



PB0FE880R Or NATURAL HISTORV IN THE ItNIVEHSlTY OF (JLAFtlOW J BON. T.R.S.E.. F.0.8. ; MEMBER 
OF THE AMERICAN PlItL080PtIICAL SOCIETY ; FELWW OF TliE BOSTON ACADEMY OF ARTS 
AKD SCIENCES ; MEMBER OF THE BOSTON NAT. BIST. aOCIETV, ETC. ETC. 



IN TWO VOLUMES 

VOL. L 



PHILADELPHIA: 

J. B. LIPPINCOTT <fc CO. 
M D C C C L V 1 1 1 



Entered aeceraiiii;- to Act of Congress, in tlie year 1H5H. by 
HKNRY DARWIN ROGKMS. 
m th" Office of tlie Clerk of the District Conrt of the Cnited 
States in and for the Eastern District of Tennsylvania. 



QE 



PREFACE. 



The Geological Survey of Pennsylvania, the chief results of which are 
embodied in this Work, was commenced early in the year 1836, in obedience to 
an Act of the Legislature authorising " A Geological and Mineralogical Survey 
of the State, &c ;" and the State Geologist was directed "to make annual reports 
to the Legislature of the progress of the Work ; and cause to be represented on 
the State Map, by colours and other appropriate means, the various areas 
occupied by the different geological formations ; and on the completion of the 
Survey, to prepare for publication a full account of the Geology and Mineralogy 
of the State." 

" By virtue of this Act the Author was appointed to conduct the Survey, 
which he actively prosecuted with a corps of able assistants for six years, until 
the appropriations were expended." " At the time of the organisation of the 
Survey, it was estimated that it would occupy at least ten years ; but the financial 
embarrassments of the Commonwealth made it expedient to withhold further 
appropriations after the sixth year, and to bring the Survey abruptly to a close 
before it could be completed in all its parts. The State Geologist, anxious to 
make the Work as full and symmetrical as possible, continued the exploration, and 
devoted himself to the preparation of the general final Report for three years 
longer, labouring for the chief part of this period without salary, and at his own 
expense." " The mass of information and material collected by the Survey, and 
thus systematised and prepared for the press, was deposited in the Office of the 
Secretary of the Commonwealth early in the year 1847, to await publication by 
the Legislature." In that position it was allowed to remain until the spring of 
1851, when, on the recommendation of a joint Committee of the Senate and 
House of Representatives, from whose Report the above statements are ex- 
tracted, funds were appointed and measures taken " for the revision of such 
portions of the field-work as, from the rapid development of the mining districts 
of the State, required re-survey, and for the publication of the Report itself, with 

VOL. I. a 



11 



PREFACE. 



the accompanying maps, plates, cuts, and sections, in a style suitable to the 
exigencies of the Work and the reputation of the Commonwealth." In the 
language of another Committee — a Select Committee of the Senate appointed 
early in 1855 to inquire into the progress and condition of the Survey, and the 
steps necessary to complete its publication — " A joint committee, consisting of 
two members of each branch of the Legislature, with the then Secretary of the 
Commonwealth, was authorised to issue proposals for a contract under which the 
publication of the Work might be made." This contract, which embraced a 
provision for further field-researches, was awarded, ill - advisedly, to wholly 
incompetent parties, who, on the eve of bankruptcy, dissolved copartner- 
shij^. The contract was allowed to j)ass to their successor, who soon after 
suspended payment." " The publishing firm which succeeded that with which 
the Committee originally contracted, was finally dissolved by the death of the 
senior partner ; and another firm took its place, which, after a short-lived exist- 
ence, soon likewise disappeared. No commercial firm then remained, even in 
name, to represent the parties with whom" the Commonwealth had contracted. 
Although the publishers had drawn, on account of their contract, the sum of four 
thousand dollars over and above the amount paid to the State Geologist (for his 
field-work, &c.), they do not appear to have made any progress towards the pub- 
lication of the Work." " The funds so advanced to the publishers, and for which 
the State has received no equivalent, are totally lost, as no sufficient security was 
taken to cover these advances." 

The Committee of the Senate making this recital, adverting to the want of 
proper management which resulted in this loss, and the delay in the publication 
of the Work, proceed to say, that " the State Geologist meanwhile commenced 
his field-work early in the spring of 1851, and continued, with a small band of 
assistants, actively engaged in it until the close of the season." " Having con- 
sumed his own means in the expectation of immediate reimbursement, he 
appealed to the Legislature for redress, which he procured." Next year " a large 
amount of material was ready for the press," and "the Geological Map was 
placed in the hands of the publishers for engraving ;" but, for the causes already 
recited, no progress was made. Notwithstanding the many impediments in his 
path, arising mainly from delays in procuring his quota of the funds, the 
Geologist persevered in his field and closet labours until the spring of 1855, 
the limit allowed by the Act of 1851. 

At that date he presented a memorial to the Legislature, calling attention to 
the bad management which had retarded the production of the large mass of 



PREFACE. 



iii 



information collected by the Survey, whereupon the Select Committee of the 
Senate already mentioned, sketching the advanced condition of the Work under 
its revised and greatly-expanded form, and presenting a Schedule of its materials, 
for the most part re-drawn and almost entirely 7'e-written, recommended " to confide 
the whole Work, in its supervision and publication, to the State Geologist him- 
self." In accordance with this suggestion, it was so enacted in March 1855 : the 
conditions of the contract between the Commonwealth and the Author being, that 
for the publication of the final Geological Report of the Survey made by him on 
behalf of the State, with the accompanying maps, plates, cuts, and engravings, 
including the enlargement of the Geological Map of the State to twice its scale, 
and the furnishing to the State of one thousand copies thereof within three years, 
he was to receive the sum of sixteen thousand dollars and the copyright of the 
Work. Fourteen thousand dollars of this fund was the amount originally allotted 
to the publication upon an estimate in 1851, made before the revision was under- 
taken, and the other two thousand were added for the enlargement of the chief 
Map. 

To save from loss a portion of the large amount of useful information col- 
lected, and to meet the expectations of the public, the Author has deemed it his 
duty to expand his Work, both in the illustrations and the text, considerably 
beyond the amount of material he proposed to print in the Schedule submitted to 
the Senate's Committee in 1855. The actual cost of the Work has, therefore, 
exceeded by several thousand dollars the amount to which he is legally entitled. 
The enlargement of the General Geological Map of the State — a task of great labour, 
amounting to a total reconstruction of it, and the introduction of much additional 
and fresh material — has itself entailed a far larger expenditure than was assigned 
it. Intended to rq:)resent, with close and faithful minuteness of detail, a country 
of excessive topographical and geological intricacy, it required its geographical 
features to be executed on copper, in the very best style of map-engraving, and 
the geological ones to be done by the beautiful modern process of colour-printing 
from stone. Both it, and the minor maps, and other illustrations executed in 
this manner, will, the Author trusts, meet the approval of his fellow-citizens and 
of his readers generally. A statement of these facts has seemed due, first, to 
the public, who have long looked for the fruits of the Survey ; and secondly, 
to the Author himself, who has encountered, in the performance of his duty, 
unusual obstacles and hardships. 

At the time the Geological Survey was organised, it was not contemplated to 
construct any new maps for the elucidation of the Geology, but simply to represent. 



iv PEEFACE. 

" by colours and other appropriate means, as the law expressed it," the areas occu- 
pied by the different geological Formations on the Map of the State, then the pro- 
perty of the Commonwealth. The Survey had not proceeded far before it was 
discovered that that Map, full of errors, was wholly unsuitable for the purpose, 
and it became apparent that a correct delineation of the Geology demanded either 
the construction of a wholly new Geographical Map, or a thorough revision and 
correction of its most defective parts, embracing the entire Mountain-chain of the 
State. This voluntary addition to the arduous labours of the Geological portion 
of the Survey was undertaken and persevered in, until a wholly new Map was 
formed — compiled in part from original Surveys, in part from the numerous explo- 
rations ordered by the State, in connection with her internal improvements — and 
was presented in 1847 as an accompaniment to the general description of the 
Geology then handed in for iDublication. In the preparation of that Map, all the 
larger features of the Mountain-chain, and of the plains and hills to the south of 
it, and of the table-lands to the north, were critically examined and laid down 
with approximate truth, though not with the refined accuracy of a trigonome- 
trical survey, upon a scale of one inch to the mile, upon two preliminary maps ; 
one embracing the region south-west of the Susquehanna, the other the country 
of the Anthracite Coal-fields between that river and the Delaware. 

Upon the revival of the Survey in 1851, reorganised more expressly for a closer 
study and exhibition of the previously less exj^lored parts of the State, especially 
the Anthracite Coal-fields, it was discovered that the Map embracing these, though 
exact enough for the general purpose which it had fulfilled, of improving this part 
of the State Map, was too inaccurate a topographical foundation for the reception of 
the very intricate geology of the region to be depicted. It became necessary, there- 
fore, to construct a new Map of the whole Anthracite country ; and this proved to be 
a very laborious and costly part of the Survey. Without any separate appropriation 
for the object, an independent instrumental Topographical Survey was carried on 
side by side with the Geological one, and the results of both embodied in a series 
of local Maps, some of them on a scale nearly as large as four inches to the mile. 
From these Field Maps the Geological and Topographical Map of the Anthracite 
Region has been carefully constructed. But for the geographical labours incidental 
to the Survey, the whole Work might have been in print years ago, and at a mate- 
rially less cost to the Commonwealth. Had the Geologist been provided, as he 
usually is in such investigations, with sufficiently truthful and large maps ready 
engraved to his hand, there would have been not only this important saving of 
time, toil, and expense, but a corresponding economy in all these particulars in the 



PREFACE. 



V 



preparation of the Work for the press, and in the supervision of it while in the 
hands of the artists. The reader will observe that all the maps which accompany 
this Work are what are called in the United States Topographical;" they picture, 
that is to say, by appropriate shading, the physical relief or inequalities of the 
surface. In this feature they embody a far larger amount of information, both 
geological and geographical, than can possibly be conveyed through geological 
charts destitute of hill-work; indeed, no map can be said to meet the wants, either 
scientific or practical, of a geological survey, which does not picture, approxi- 
mately at least, the vertical element as well as the horizontal. Every Physical 
Geographer, every Engineer, indeed every working Miner, will testify to the correct- 
ness of this assertion. Partly for this reason, and partly through the necessity 
for making new and more accurate maps of some sort, whereupon to present the 
Formations of the State, the Author thought it best, while conducting the two- 
fold Survey, to knit together the Geology and the Topography as intimately as the 
means at his disposal would permit. 

In the Palffiontological portion of this Work two principal objects have been 
kept in view ; first, to exhibit the most characteristic organic remains of the 
fossiliferous formations of the State ; and secondly, to ascertain, describe, and 
figure all the more prominent new species found in the Carboniferous Rocks, 
especially in the Coal-formation proper. The fossils of the various deposits have 
been carefully examined and compared, and due weight has been assigned them 
in the classification and grouping of the strata ; but as a thorough Palseontological 
exploration did not enter into the plan of the Geological Survey of the State, 
being precluded by the stintedness of the funds appropriated, the Author has 
contented himself with introducing only so much of the subject as will fully illus- 
trate the typical nature of the ancient forms of life entombed within the different 
formations, except in the instance of the extinct vegetation of the Coal. Even 
had he been allowed the funds to conduct an independent Pal?eontological investi- 
gation, a large portion of the labour might have seemed superfluous, from the 
circumstance that the neighbouring State of New York, far richer than Pennsyl- 
vania in well-preserved organic remains, including, moreover, most of the same 
species, has for many years past been conducting, at great expense, a thoroughly 
minute investigation of its Fossils — extending, indeed, to other States — by the 
ablest Palaeontologist of the country. Professor James Hall. I am indebted to my 
accomplished Assistant, Leo Lesquereux, Esq., for the valuable essay and beauti- 
ful figures illustrating the new species of Coal Vegetation, discovered chiefly by 
himself in the Anthracite Coal-fields of the State. 



VI 



PREFACE. 



The intimate relations of the Geology of Pennsylvania to that of the whole 
Appalachian Basin, or the region between the Atlantic Slope of the Continent 
and the Central Plains west of the Mississippi, and the importance of co-ordi- 
nating its strata, especially its Coal-rocks, with those of other districts, the better 
to illustrate its true position industrially as well as physically, have induced me 
to introduce a somewhat full Essay on the General Geology of the United States. 
It is intended to fulfil the office of a key to the more minute descriptions 
contained in the main body of the Work — to be to the Geology of the State what 
a general map on a small scale is to a local one greatly amplified ; or w^hat a 
" Finder Telescope," embracing a wide field of view, is to the chief instrument 
directed upon a special star, the general j^/ace of which the other shows. 

A like motive — a desire to indicate the positions occupied by the several 
widely-diffused Formations of Pennsylvania and the United States in the general 
scale of the strata best known to the geological world (I mean the scale of the 
European Rocks) — has impelled me to add an Essay, originally presented in 
abstract to the British Association, " On the Correlation of the American and 
British Palaeozoic Strata." It is only through such wide comparisons, cautiously 
instituted, that we can learn with what portions of the world our country is in 
nearest affinity. 

In the Appendix to this Work there appears, amid other miscellaneous matter, 
a description of the methods of research employed in the Geological Survey of 
Pennsylvania, with some suggestions in relation to geological explorations gene- 
rally, adapted to other countries. 

The nomenclature of the Palaeozoic Formations employed in this Work 
demands a word of explanation here. After a mature analysis of the whole 
system of Ancient Secondary (Palaeozoic) Rocks embraced in the Aj^palachian 
Chain, conducted in accordance with their organic remains and mineral com- 
position, it became apparent to the State Geologists of Virginia and Pennsyl- 
vania, Professor W. B. Rogers and myself, that none of the existing systems of 
nomenclature — neither the imported British ones, nor the narrowly local geo- 
graphical ones of New York — were applicable to our strata, under the average 
types they manifest in the mountain-chain and the broad basin of the States to the 
West of it. It was found that these Appalachian Rocks were far from being suffi- 
ciently co-ordinate with the European Palaeozoic strata, under their British types, 
to bear their names ; while, on the other hand, the special titles assigned to them 
in New York w^ere deemed too local and too inexpressive, either of their position 
in the scale of Formations, or of their ruling characters, to be usefully applicable. 



PREFACE. 



Vll 



The fifteen Formations, or series of deposits, defined by their prevalent organic 
remains, and of the physical horizons which separate them as sediments, extending 
from the lowest deposited in the dawn of animal life to those formed at the end 
of the Coal Period, are called by names significant of their relative ages, the 
words employed suggesting metaphorically the different natural periods of the 
day. These names are — Primal, Auroral, Matinal, Levant, Surgent, Scalent, Pre- 
meridian, Meridian, Post-meridian, Cadent, Vergent, Ponent, Vespertine, Umbral, 
and Serai, meaning respectively the Formations of the Dawn, Daybreak, Morning, 
Sunrise, Mounting Day, Climbing Day, Forenoon, Noon, Afternoon, Declining 
Day, Descending Day, Sunset, Evening, Dusk, and Nightfall. Some such 
nomenclature, based on time, is, for many reasons, preferable to the inexpressive 
ones which rest for the most part on geographical terms, only locally correct, or 
on narrow and inconstant palieontological characters. 

I avail myself of this opportunity to express my ever-grateful and affectionate 
acknowledgments to my brother. Professor William B. Rogers, for the valuable 
assistance he has generously rendered the Survey in every department at various 
stages of its progress. 

The staff of Assistants on the Survey of the State necessarily fluctuated with 
the vicissitude of its history, and the changing demands of the work. Small at 
the commencement, it was rapidly augmented to a corps of twelve, which it 
remained till towards the suspension of the appropriation in 1842 ; after which, 
until 1845, whatsoever aid I required was chiefly employed on my own account. 
Upon the resumption of the field-work in 1851, a new staff was organised, 
consisting of two Geological Assistants, a Topographer, Assistant Topographer, 
and a party of Surveyors. 

In the campaign of 1836 the assistants were John F. Frazer (now Professor 
Frazer), and James C. Booth (since Professor Booth). In that of 1837 they were 
Messrs Samuel S. Halderman, Alexander M'Kinley, Charles B. Trego, and James 
D. Whelpley, Geologists ; and Dr Robert E. Rogers, Chemist. 

In that of 1838 they were Messrs Harvey B. Holl, Alexander MTvhiley, 
Charles B. Trego, James D. Whelpley, James T. Hodge, Dr Robert M. Jackson, 
John C. MTCinney, Peter W. Shaeffer, and Townsend Ward, Geologists ; and Dr 
Robert E. Rogers, and Martin H. Boye, Chemists. 

In that of 1839 the corps was nearly the same, Mr Peter Lesley and Dr Hen- 
derson being added, and Messrs Whelpley and M'Kinney resigning. 

In 1840 the corps consisted of the same assistants, with the addition of an able 
Draftsman, George Lehman. 



viii 



PEEFACE. 



In 1841 the number of the Geological Staff was reduced, the Geologists being 
Mr M^Kinley, Mr Holl, Dr Jackson, Mr Lesley, and Mr Boye ; and the Chemist, 
Dr Rogers. 

After the revival of the field-work in 1851, the Geological Assistants were Pro- 
fessor E. Desor and William B. Rogers, junior. The Topographers were Peter 
Lesley, and subsequently Augustus A. Dalson ; and the chief Surveyors, Peter 
W. Shaeffer (performing also geological functions) and Henry W. Poole. The 
neat one-sheet Map of the Coal-fields is by Mr Lesley. The beautiful large Map 
of the Anthracite Region is by Mr Dalson, chiefly from his own surveys. 

Since the cessation, in the autumn of 1854, of the active revision of the Min- 
ing Districts, and of the Topographical Surveys, my sole assistant in geological 
field-research, in completing unfinished toj^ograj^hical work, and in preparing for the 
press the final Drawings of the extensive mass of Geological Sections and Diagrams 
introduced into this book, has been my ne^^hew, William B. Rogers, junior. 

Besides the gentlemen here mentioned as scientific assistants, the Survey has 
employed many other persons, some of them of much skill and merit, in sub- 
ordinate capacities. One of these, Patrick Daly, merits especial mention for the 
value of his services and fidelity to the Survey. 

For full mention of the special parts performed by the individual members of the 
corps in the various successive stages of the Survey, I beg to refer to the widely- 
circulated Annual Reports of its progress. To attempt a precise history of the 
labours of each, in a field where their duties were so multifarious, would, besides 
being somewhat invidious, lead me into too minute and tedious a narrative. 

I beg, in concluding this Preface, to testify in general terms my high appre- 
ciation of the zeal and ability of my Assistants, my admiration of their energy in 
confronting difficulties, and their fortitude in meeting the privations and hard- 
ships incident to the life of a Geologist in the United States ; and my grateful 
thanks for tlie personal devotion displayed by all of them, with one or two 
exceptions, in aiding me to the fulfilment of my duties. 

HENEY D. ROGEES. 



PHnADELPHiA, April 1858. 



TABLE OF CONTENTS. 



INTRODUCTION— PHYSICAL GEOGEAPHY. 

PAGE 

Physical Geography of Pennsylvania, . . 1 

Boundaries and area, .... 1 

Position of the state, .... 2 

General watershed and main slopes, . . 2 

Chief natural divisions, .... 3 

Orography and scenery of the first district, . 4 

Orography and scenery of the second district, . 5 

Appalachian ridges, . . . . 7 
Mountain ridges, . . . .10 

1. Anticlinal ridges, . . . .11 

2. Synclinal ridges, .... 12 

3. Monoclinal ridges, .... 13 
Valleys, . . . . . .15 

1. Anticlinal valleys, . . . . IfJ 

2. Synclinal valleys, . . . .17 

3. Monoclinal valleys, ... 18 
DifiFerent classes of scenery in the mountain-chain, 

and their relationships to the physical geography 

and geology of the region, . . . 19 

Scenery commanded by anticlinal mountains, . 19 

Scenery from synclinal mountains, . . 22 

Views from the ends of the exterior basins, . 23 
Views from the ends of the interior troughs or 

coal basins, ..... 24 

Scenery and structure of the mountain crests, . 25 

1. Anticlinal crests, .... 25 

2. Synclinal crests, .... 26 

3. Monoclinal crests, .... 26 
Aspects of the mountain sides, ... 27 
Passes or notches in the mountains, . . 28 

^Xxeneral character of the scenery in the valleys of the 

Appalachian zone, .... 30 

Anticlinal valleys, . . . . 30 

Synclinal valleys, .... 30 
Monoclinal valleys, . . . .31 
Scenery characteristic of the broad valleys of com- 
plex structure, . . . .31 

Orography and scenery of the third district, . 32 

1. South-eastern belt of the bituminous coal 

region, ..... 33 

2. Northern belt of the bituminous coal-field, . 34 

3. Basin of the Alleghany and Ohio rivers, . 30 
Orography and scenery of the fourth district, . 36 
Lakes, ...... 37 

Orography and scenery of the fiftli district, . 39 

Hydrography, ..... 39 

Atlantic drainage, . . ... 40 

Its general periphery, . . ^ . . 40 
Its chief river basins and their dividing water- 
sheds, ..... 40 

VOL. I. 



PAGE 

Areas of the chief river basins, . . . 41 

Mexican Gulf, or Ohio river drainage, . 42 

The lake drainage, .... 42 

River system of the Delaware river, . . 43 

River system of the Susquehanna river, . . 44 

River system of tlie Potomac river, . . 45 

River system of the Alleghany river, . . 40 

Scenery along the principal rivers, . . 47 

The Delaware river, .... 47 

The Susquehanna river— north branch, . 48 

West branch of Susquehanna, ... 49 

The Juniata river, .... 50 
The Alleghany river, . . . .51 

Climatology of Pennsylvania, ... 52 

Temperature — average of the year, . . 53 

Mean temperature of the spring months, . 53 

Summer mean temperature, ... 53 

Autumn mean temperature, ... 54 

The winter mean temperature, ... 54 

Summary, ..... 54 
Extremes of temperature, . . .54 
Tabular statement of greatest degrees of heat and 

cold, over a term of nearly 60 ^ears, . 55 

Rain averages for the year, ... 56 

Extreme quantities of rain, ... 56 

Prevailing winds, .... 57 

GEOLOGY. 

GENERAL INTRODUCTORY CHAPTER. 

Classes of rocks embraced in Pennsylvania, . 59 

The gneissic or hypozoic rocks, ... GO 

The palaeozoic rocks, .... 60 

PART I. 

METAMORPHIO STRATA OF PENNSYLVANIA. 

INTEODUCTOEY CHAPTER. 

Classification of the metamorphic strata of the Atlan- 
tic slope of the middle and southern states, . 62 

BOOK I. 

GNEISSIC ROCKS OF PENNSYLVANIA. 

General distribution of the gneissic or ancient meta- 



morphic strata, . 
The three gneissic districts, 



66 
66 



TABLE OF CONTENTS. 



CHAPTER I. 

SOUTHERN ZONE OF GNEISS. 



Or Gueissic rocks south of the Montgomery and 

Cliester valley, ..... G7 

DETAILS OF THE SOUTHERN GNEISSIC DISTRICT. 

Gneissic rocks of the valley of the Schuylkill, between 

Philadelphia and Spring Mill, ... 67 
First belt, ...... 68 

Granite veins, ..... 69 

Unstratified or true igneous rocks, . . 69 
Syenite, ...... 69 

Trap dykes, . . . . .70 

Falls of Schuylkill quarry, . . .70 

Second or middle belt, . . . .71 

Wissahickou Creek section, ... 72 
Third or northern belt, .... 73 

Description of the northern or upper belt of gneiss, 73 
Structure of the upper or northern belt of gneiss, . 74 



Subdivisions and details of the northern belt of gneiss 

on the Schuylkill, .... 75 

Limits of the three belts of gneiss of the southern 
gneissic district, &c. Limits of the southern 
belt, ...... 76 

Limits of the mica slate or middle gneissic belt, . 77 
Limits of the northern belt of the southern gneissic 
district, ...... 77 

Of the geological structure of the gneissic region of 



the Schuylkill, (see the Section), . . 78 
Of the belt of gneiss north of the Mooretown and 

Attleborough range of Primal sandstone, . 80 

Old plumbago mine. Bucks county, . . 81 
Narrow ranges and local outcrops of gneiss west of 

the Brandy wine Creek, . . . 81 
Southern belt, . . . . .81 

Middle belt of gneiss on the Brandywine, . 82 

Northern belt of gneiss near the Brandywine, . 82 



CHAPTER II. 

MIDDLE ZONE OF GNEISS. 

Or the gneissic rocks between the North Valley Hill of 



Chester county, and the southern margin of the 

middle secondary red sandstone, . . 83 

Boundaries, ..... 83 

Character of the gneiss rocks north of the Chester 

county valley, ..... 85 

Of the undulated structure of the gneiss district 

north of the Chester county valley, . . 85 1 

Faults, ...... 86 

Iron ores of the gneiss, .... 87 

Brown iron ore, or htematite of the basin of Pick- 
ering Creek, near the Yellow Springs, and the 

geological conditions under which it occurs, 87 

Lewis's ore bank, .... 87 

Fegeley's ore beds, near Yellow Springs, . 88 

Ore-deposits south-west of Yellow Springs, . 89 

Latschaw mine, ..... 89 

Steitler ore bank, .... 89 

Jones' mine, near Yellow Springs, . . 89 

Iron ore in Uwchlan township, . . 90 



CHAPTER III. 



NORTHERN ZONE OF GNEISS. 

PAOK 

Or gneissic rocks north of the niesozoic red sandstone, 91 

Gneissic rocks of the South mountains, . . 91 

Boundaries, ..... 91 
Geographical range of the rocks of the South 

mountains, ..... 91-92 
Millbaugh hill, ..... 93 
Composition and structure, ... 93 
More detailed description of the gneiss and its mine- 
rals in the South mountains, ... 94 
Ridges south of the Lehigh, ... 96 
Stratification of the South mountains as seen in 

transverse local sections, ... 98 

Delaware river, west side, ... 98 

Unconformity of the primal strata to the gneiss, 99 

Durham hill, ..... 99 
Unconformable contact of the jirimal rooks and 

the gneiss, ..... 100 

Mountains between Allentown and Coopersburg, ] 00 
South mountains, 9 miles E. of Reading, through 

Friedensburg, . . . . .102 
Neversink hill of the South mountain, near Read- 
ing, ...... 103 



PART II. 

PALEOZOIC OR ANCIENT FOSSILIFEROUS STRATA 
OF PENNSYLVANIA. 

INTRODUCTOEY BOOK. 
CHAPTER L 



A synopsis of the Appalachian palisozoic strata of Penn- 
sylvania in the ascending order,, . . 104 

Primal series, ..... 104 
Primal conglomerate, .... 104 
Primal older slate, .... 104 
Primal white sandstone, . . . 104 

Primal upper slate, .... 104 

Auroral series (blue limestone of the western states), 105 
Auroral calcareous sandstone, . . . 105 
Auroral magnesian limestone, . . .105 

Matinal series, . . . . .105 

Matinal argillaceous limestone, . . . 105 

Matinal black slate, . . . .105 

Matnial shales, . . . . .105 

Levant series, . . . • .105 

Levant grey sandstone, . . . .105 

Levant red sandstone, .... 105 
Levant white sandstone, . . .105 

Suvgent series, . . . • .106 

Surgent Lower slate, . . . .106 

Surgent iron sandstone, . . . .106 

Surgent upper slate, .... 106 
Surgent lower ore shale, . . . 106 

Surgent ore sandstone, .... 106 
Surgent upper ore shale, . . . 106 

Surgent red marl^ . . . .106 

Scalent series, . . . . .106 

Scalent variegated marls, . . . 106 



TABLE OF CONTENTS. xi 



Scalent grey marls, . . . .106 
Scalent limestone, .... 107 

Pre-meridian series, .... 107 
Pre-meridian limestone, . . .107 

Meridian series, ..... 107 
Meridian slate, . . . . . 107 
Meridian sandstone, .... 107 

Post-meridian series, . . . .107 

Post-meridian grits, .... 107 
Post-meridian limestone, . . . 107 

Cadent series, . . . . .107 
Cadent lower black slate, . . .107 
Cadent shales, . . . . • . 108 

Cadent upper black slate, . . . 108 

Vergent series, . . . . .108 
Vergent flags, ..... 108 
Vergent sh'ales, . . . . .108 

Ponent series, ..... 108 
Ponent red sandstone, . . . .108 

Vespertine series, . . . . .108 
Vespertine conglomerate and sandstone, . 108 

Umbral series, ..... 108 
Umbral red shales and limestone, . . 108 

Serai series, . . . . .109 

Serai conglomerate, . . . .109 
Lower productive coal-measures, . . 109 
Lower barren coal shales, . . . 109 
Upper productive coal-measures, . . 109 
Upper barren coal shales, . . .109 

CHAPTER IL 

Subdivisions of the Palseozoic region, and brief sketch 
of their structural features, . . .110 

First District, ..... Ill 
First belt, ..... Ill 
Second belt, . . . . .111 
Third belt, ..... Ill 
Fourth belt, . . . . .111 
Fifth belt, ..... 112 
Sixth belt, . . . . .112 

Second District . . . . .112 

Kittatiny Valley, . . . .112 

Third District, ..... 113 
Orwigsburg and Stroudsburg Valley, . . 113 

Fourth District, . . . . .113 
The north-eastern counties, . . . 113 

Fifth District, . . . . .114 
The mountain-belts of the Lower Juniata, . 114 
The first anticlinal belt, . . . 114 

The first synclinal belt, . . .114 

The second anticlinal belt, . . .114 
The second synclinal belt, . . . 114 

The third anticlinal belt, .... 115 
The third synclinal belt, . . . 115 

The fourth synclinal belt, . . . 115 

Sixth District, . . . . .116 

The mountain-belts of the Upper Juniata and 

west branch of the Susquehanna, . . 116 

The first belt, ..... 116 
The second belt, , . . .116 

The third belt 116 

The fourth belt, . . . .117 
The fifth belt, 117 



Seventh District, . , . . .117 
The country N.W. of the bituminous coal region, 117 

Eighth District, . . . . .117 
The anthracite coal region, . . . 117 
The first belt, . . . . .118 

The second belt, . . . .118 

The third belt, 118 

The fourth belt, . . . .118 
The fifth belt, 119 

Ninth District, ..... 119 
The bituminous coal region, . . . 119 

The first basin, 120 

The second basin, . . . .120 
The third basin, . . . .120 

The fourth basin, . . . .120 

The fifth basin, 120 

The sixth basin, . . . .120 

CHAPTER in. 

Distribution of the Palajozoic strata in Pennsylvania, 

and their changes of type and thickness, . 122 

Primal series — South of Chester county valley, 122 
Primal lower slate, .... 122 
Primal sandstone, . . . .122 

Primal upper slate, .... 122 

Primal series — in the South mountains, . 123 

Auroral series, . . . . .123 
Auroral calcareous sandstone, . . . 123 
Auroral magnesian limestone, . . .124 

Matinal series, ..... 124 
Matinal limestone, .... 125 
Matinal slate, ..... 125 
Matinal shales, . . ^ . . 125 

Levant series, ..... 126 
Levant grey sandstone, . . . 126 

Levant red sandstone, . . . .128 
Levant white sandstone . . ~ . 129 

Surgent series, . . . . .131 
Surgent lower slate, .... 131 
Surgent iron sandstone, . . . 132 

Surgent upper slate, . . . .132 
Surgent lower shale, . . . .133 
Surgent ore-sandstone, .... 133 
Surgent upper shale, . . . .133 
Surgent red shale, .... 134 

Scalent series, ..... 134 
Scalent variegated marls, . . . 135 
Scalent grey marls, .... 135 
Scalent limestone, .... 135 

Pre-meridian series, .... 136 

Pre-meridian limestone, . . • 136 

Meridian series, ..... 137 
Meridian slate, ..... 137 
Meridian sandstone, .... 137 

Post-meridian series, .... 138 

Cadent series, ..... 138 
Cadent lower black slate, . . .138 
Cadent shales, ..... 139 
Cadent upper black slate, . . .139 

Vergent series, . . • • .140 

Vergent flags, . . . . .140 

Vergent shales, . . . • .141 

Ponent series, . . • • • 1-11 



TABLE OF CONTENTS. 



PAGE 

Vespertine series, ..... 142 
Umbral series, . . . . .144 
Serai series, ..... 146 



BOOK I. 

PEIMAL AND AURORAL STRATA OF THE 
ATLANTIC SLOPE. 

DIVISION I. 

Primal series, . . . . .149 
Introduction, . . . . .149 

CHAPTER I. 

Primal series — The southern belt, . . . 150 
Range of the southern trough of primal rocks in Bucks 
and Montgomery counties, . . . 1.51 
Primal Sandstone — S. of Attleborough, . . 152 
Principal quarries in the southern belt of primal sand- 
stone between the Neshaminy and the Pennypack, 153 
General geographical limits of the primal strata W. of 
the Schuylkill, and S. of the Chester county lime- 
stone valley, ..... 153 
Composition of the primal strata as they are developed 
in the Montgomery county valley, E. of the Schuyl- 
kill river, ..... 154 
Localities where the primal rocks may be best studied, 156 
Aramink Creek, ..... 156 
Composition of the primal strata in their distribution, 

W. of the Schuylkill, .... 156 
Primal white sandstone, .... 156 
Primal slates, ..... 156 
Description of the section along the Brandywine, (see 

engraved Section), .... 158 

The primal strata, as embraced in the synclinal valley 

of Montgomery and Chester counties, . . 158 
Structure of the eastern end of the limestone basin of 
Montgomery and Chester, from the Wissahickon to 
the Pennypack, ..... 159 
Details respecting the primal rocks in the district of 

AVillow Grove, (see Sections), . . . . 160 

Primal strata within the auroral limestone valley of 

Montgomery and Chester counties, . . 161 
First anticlinal lifting the primal rocks, . . 161 

Overturned outcrop of primal sandstone in a quarry 

in Barren Hill, on the Ridge Road, . . 162 
Second anticlinal of primal rocks, . . . 162 

Third anticlinal of primal rocks, . . .163 

Fourth anticlinal of primal rocks, . . . 163 

Bethlehem Turnpike from Sandy Run to Chestnut 

Hill, 164 

Passage from the primal to the auroral strata, at Spring 
Mill and Conshohocken, on the south side of the 
limestone basin, . . . . .164 
Description of section across the southern side of the 
limestone basin of Montgomery, being a continua- 
tion of the section along the Schuylkill from Phila- 
delphia to Spring Mill, . . . .164 
Passage beds at the mouth of Matsan's Run, opposite 
Conshohocken, ..... 165 
The primal white sandstone bounding the Chester 
county valley west of the Schuylkill, . . 1G5 



The southern outcrop of the primal sandstone, . 166 
Belts and localities of serpentine south of the lime- 
stone valley of Montgomery and Chester coun- 
ties, ...... 167 

1. The serpentine and steatite range of the Schuyl- 

kill in the southern edge of Montgomery 
county, . . . . .167 

2. Second outcrop of serpentine in our progress 

westward, . . . . .168 

3. Tliird belt of serpentine, or that of the neigh- 

bourhood of the Paoli, . . .168 

4. Fourth tract of serpentine, . . . 169 

5. Fifth serpentine tract. West Chester Barrens, 169 

6. 7, 8, 9, 10, 11. Outcrops of serpentine and 

steatite, . . . . .169 
12, 13, 14, 15, 16. Outcrops of serpentine and 

steatite, . . . . .170 
17. Serpentine belt of the Union ville Barrens in 

Newlin Towoiship, . . . 170 

Long serpentine belt of the State Line on the southern 

edge of Chester and Lancaster counties, . 170 
The line mine, . . . . .171 
Titaniferous iron ores, . . . .171 

CHAPTER II. 

The primal series bounding the middle gneissic dis- 
trict, ...... 173 

Primal series, wldte sandstone and slates in the 
North Valley HiU, .... 173 

Diamond Rock to Paoli, . . .175 

North of Coatesville, .... 175 

Hill north of Parkesburg, . . . 175 
Fossils in the primal rocks in Pennsylvania, . 176 
Middle belt of primal rocks north of the limestone 

valley, or that of Mine Ridge and it spurs, . 176 
Northern ridge of jirimal rocks north of the Chester 

county valley, Welch moimtain, &c., . . 178 
Insidated anticlinal ridges of i)rimal sandstone, . 179 
Insulated basin of sedimentary strata within the 

northern gneissic area of Chester coimty, . 179 
Composition and limits of the primal series of the 
North Valley Hill, near Valley Forge, and west- 
ward, 180 

Iron ores of the primal strata, . . . 181 
Iron ore bank of Chestnut Hill near Columbia, . 182 
Iron ore at the base of the primal slate. Chestnut Hill 
mine, ...... 183 

CHAPTER III. 

Primal strata on the Susquehanna and in York county, 184 

Description of the Susquehanna section, . . 184 

Primal rocks along the Susquehanna river, . 185 

Primal rocks from Lockport to Shenck's Ferry, . 186 

M^Call's Ferry, 187 

Slate belt of Peach Bottom, . . .188 

Statistics of slate belt ; the price of slate, . 189 

Serpentine belt, ..... 190 

Gneiss and granite belt, .... 190 

Intrusive rocks, ..... 190 

Exception to the prcvaiUng law of cleavage, . 190 

Primal series, or slate belt in the southern part of York 

county, ...... 191 



I 



TABLE OF 



Chiques Ridge, . . ■ • . . 193 
Section from Columbia to the Chiquesalimga Creek 

at Haldeman's through the Chiques Ridge, . 193 
Pigeon Hills, 195 

CHAPTER IV. 

Primal rocks of the South mountains between the Dela- 
ware and Schuylkill, .... 196 
In Berks county, . . . . .196 

In the hills east of Reading, . . . 197 
Iron ores of the primal strata, . . .201 

Outlying belt of primal rocks on Millbough Hill, . 202 

CHAPTER V. 

South Mountains, south-west of the Susquehanna, . 203 
Sections of the strata, .... 205 
Gettysburg railroad, .... 206 

DIVISION II. 
Auroral series, ..... 208 

CHAPTER I. 

General description of the limestone valley of Mont- 
gomery and Chester, .... 209 

Northern and southern boundaries of the limestone, 209 
Chemical composition, .... 210 

Geological structure, . . . .211 

Trough-like dip of the limestone, . . 211 
Conditions of metamorphism of the limestone, . 212 
Quarries in the limestone, and other practical de- 
tails, . . . ... .213 

Trap dykes, . . . . .214 

Of the marble of the limestone basin of Montgomery 
county, . . . . . .215 

Localities and statistics of the iron-ore banks of the 
limestone basin of Montgomery and Chester coun- 
ties, ...... 216 

Insulated limestone basins in the primal rocks of 
Lancaster county, and their deposits of iron ore, 217 
Iron ores, ..... 218 

Rotlifon ore bank, Safe Harbour, and Gantner ore 
bank,. ..... 218 

Ore ground, east side of Conestoga Creek, Safe 
Harbour, . . . . .218 

Local limestone basins, .... 219 

CHAPTER II. 

Auroral limestone of Lancaster and York counties, . 220 
Trap dykes, (fee, . . . . .221 

Auroral limestone in the valley of York, . . 222 
Iron ore, ...... 222 

Limestone, ..... 223 

Auroral limestone at the southern base of the South 
mountain, in Adams county, . . . 223 

Small insulated belts and quarries of limestone south 

of the middle secondary red sandstone, . . 224 

Limestone quarries of Chester county, south of the 
Great valley, ..... 225 

Belt first— Brown's quarry, . . . 225 

D. Nevins's quarry, . . . 225 

J. Nevins's quarry, . . . 225 

Belt second (or that of Kennet Square), . . 226 



CONTENTS. , xiii 

PAGE 

Belt tliird, 226 

Uplifts of gneiss and dykes of granite, . 227 

Granite dykes, ..... 228 

Belt fourth, 229 

Belt fifth, 230 

Belt sixth, 231 

Insulated localities of crystalline limestone within the 
gneissic district, north of the Chester county 
valley, . . . . . .231 

CHAPTER III. 

Auroral limestone of the South mountains between the 

Delaware and Schuylkill, . . . 233 

Durham cave, ..... 236 

Zinc mine of the Saucon, .... 236 

BOOK II. 

THE KITTATINNY VALLEY, OR THE SECOND 
PALEOZOIC DISTRICT. 

CHAPTER L 



Boundaries and features of the valley, and character of 



the strata, ..... 


237 


Dimensions, ..... 


237 


Cleavage, ...... 


237 


Character or type of the fonnations. 


238 


The auroral magnesian limestone, 


238 


The matinal limestone, .... 


239 


Matinal black slate and matinal limestone on Mar- 




tin's Creek, ..... 


239 


The matinal black slate, .... 


239 


The matinal newer slate, .... 


239 


Organic remains, ..... 


240 


Geological structure, .... 


240 



CHAPTER II. 

Auroral limestone of the Kittatinny valley, from the 

Delaware to the Schuylkill, . . . 241 
At the Delaware river, .... 241 
North of Chestnut Hill, . . . .242 

Section from Easton, north along the Delaware, includ- 
ing the mineral axis of Chestnut Hill, . . 242 
Anticlinals, ..... 244 

Cleavage in the region of the Delaware river near Eas- 
ton, and the South mountains, . . . 244 

CHAPTER in. 



Matinal slate of the Kittatinny valley, between the 



Delaware and Schuylkill, 


246 


Boundaries, ..... 


246 


Geological structure of the district, 


24G 


Slaty cleavage, ..... 


247 


Roofing slate quarries near Delaware water-gap, 


247 


Slate quarries near the Lehigh water-gap. 


248 


Evidences of erosion of the surface, 


249 


Hydraulic lime, ..... 


249 


Slate hills ; red slate ; band of limestone. 


249 



CHAPTER IV. 

Auroral limestone of the Kittatinny valley, between 
the Schuylkill and Susquehanna rivers, . 251 



« 



TABLE OF 



Trap dyke, . . . ... .251 

Iron ores, . . . . . .251 

CHAPTER V. 

Matiual slate of the Kittatinny Valley, between the 

Schuylkill and Susquehanna, . . . 252 

Details, ...... 253 

Iron ore, ...... 254 

Limestone, ..... 254 

Bunker's Hill, 254 

The Hole mountain, .... 255 

Matinal slate, Kittatinny valley, . . . 256 

CHAPTER VI. 

Auroral limestone of the Kittatinny valley, between 
the Susquehanna and the Maryland State Line, 257 
Boundary of auroral limestone and matinal slate, 257 
Boundary of auroral limestone and primal slate, 258 
Details of auroral limestone, . . . 259 

CHAPTER VIL 

Principal belt of the matinal slate of the Kittatinny 
valley, between the Susquehanna and the Maryland 
State Line, ..... 260 
Boundary, ...... 260 

CHAPTER VIII. 

Belts of auroral limestone and matinal slate in the 

south-western part of Franklin county, . 261 

First limestone belt, .... 261 
First slate belt, . . . . .261 

Second limestone belt, . . . . 261 

Second slate belt, ..... 262 

Third limestone belt, .... 262 

Third slate belt, ..... 262 

CHAPTER IX. 

Iron ores of the Kittatinny valley, . . . 263 
Iron ores between the Lehigh and the Schuylkill, . 263 
Balliot's mines, ..... 264 
Trexlerstown mines, .... 265 
Copperas mine, ..... 265 
Result of borings at the iron and copperas mines 

near Trexlerstown, .... 265 
Between the Schuylkill and the Susquehanna, . 266 
Iron ores between the Susquehanna river and the Mary- 
land State Lme, ..... 266 

BOOK III. 

District of the Orwigsburg and Stroudsburg valley, 270 
CHAPTER I. 

Limits of the district, and character of the formations, 270 

Character of the strata in the district, . . 271 

Description of the strata from the Delaware water-gap 

northward to Broadhead's Creek, . . 271 

Levant rocks, Kittatinny mountain, . . 271 

Surgent strata, ..... 272 

Pre-raeridian limestone series, . . . 272 

Meridian sandstone series, . . . 273 

Post-meridian series, .... 273 

Cleavage near the Delaware water-gap, . . 273 



CONTENTS. 



Description of the strata from the Lehigh gap north- 
ward, ...... 273 

Levant series, ..... 273 

Surgent series, ..... 274 

Section on the Lehigh from south side of Stone ridge 

northward — details, .... 274 

Description of the strata at the Susquehanna gap in 
Kittatinny mountain, (see Section east side of river), 276 

Variations of type in the line of outcrop, . 276 

Levant series, ..... 276 

Levant white and grey sandstones, . . 277 

Surgent slates and shales, . . . 277 

Surgent red and scarlet variegated shales, . 277 

Pre-meridian limestone, . . . 278 

Meridian sandstone and shales, . . 278 

Post-meridian grits and Umestone, . . 279 

Post-meridian limestone, . . . 279 
The cadent strata, . . . .279 

CHAPTER II. 

Region from Carpenter's Point to Walpack Bend, 280 

CHAPTER III. 

From the Walpack Bend to the Delaware water-gap, 281 

South-west of Walpack Bend, (see Section), . 281 

CHAPTER IV. 

Strata from the DelaAvare water-gap to the wind-gap, 283 

The levant white sandstone strata, . . 283 

The surgent red shales, .... 283 

The pre-meridian limestone, . . . 283 

The meridian sandstone, .... 284 

Details— Godfrey's ridge, .... 284 

The vergent flags, ..... 285 

Ponent series, ..... 286 

CHAPTER V. 

From the wind-gap to the Little Schuylkill, . 287 
Flexures at wind-gap and at Lehigh water-gap 

compared, ..... 287 

Valley N. of the Kittatinny mountain, . . 288 

Stone ridge at the Lehigh, . . . 288 

CHAPTER VL 

From the Little Schuylkill to the Swatara, . 289 

Little Schuylkill through Post Clinton, . . 290 

Surgent series, ..... 290 

Scaleut limestone, .... 291 

Schuylkill haven, ..... 291 

Pre-meridian and meridian series, . . 291 

Ponent, vespertine, umbral, and serai rocks, . 291 

Schuylkill through Summer hill, . . . 292 

Blue and Second mountains, . . . 292 

CHAPTER VIL 

From the Swatara to the Susquehanna, . 293 

BOOK IV. 

FOURTH OR NORTH-EASTERN DISTRICT. 

Boundaries, &c., ..... 294 



TABLE OF CONTENTS. 



XV 



CHAPTER I. 



Strata included in the North-eastem district, . 294 

Vergent series, . . . . . 294 

Vergent flags, ..... 295 

Tliickness, 295 

Lithological features, .... 295 

Ripple marks, ..... 295 

Diagonal lamination, .... 296 

Organic remains, .... 296 

Vergent shales, ..... 297 

Thickness, 297 

Lithological features, .... 297 

Features of deposition, .... 298 

Organic remains, .... 298 

Poneut series, ..... 299 

Lithological composition and tliickness, . 299 

Organic remains, .... 300 

Vespertine conglomerate, .... 301 

Lithological composition and thickness, . 301 

Organic remains, .... 302 

CHAPTER II. 

Structure and local details of the South-eastern division 

of the district, ..... 303 

Local details, ..... 304 

CHAPTER III. 

Structure and local details of the North-eastern di- 
vision of the fourth district, . . . 305 
Local details, ..... 306 

CHAPTER IV. 

Structure and local details of the western division of 

the fourth district, .... 307 

Topography, ..... 307 

Anticlinal axes, ..... 307 

Local details, ..... 309 

The Narrows of the Susquehanna, . . .310 

Limestone boulders, .... 310 

Strata East of the Tioga river, . . . 310 

Tioga river and country westward, . . . 310 
Vergent shales, . . . . .310 
Iron ore stratum, . . . . .311 
Roseville on Mill creek, . . . .311 
Ponent red shale, . . . . .311 

Limestone of the Vespertine series, . . 311 

Mountain escarpment S. of Wellsborough, . 312 
Singular lake, . . . . .312 

BOOK V. 

Fifth or Lower Juniata district, being the South- 
eastern half of the Appalachian chain between 

the Susquehanna and Maryland, . . 313 

DIVISION I. 

First and second synclinal, and included anticlinal 
belts, embracing Perry and the North-western 

portion of Franklin county, . . . 313 



CHAPTER L 
Structure of Perry and western part of Franklin 



county — Sherman's valley, . . . 313 
Flexures in the strata of Sherman's valley, . . 314 
Anticlinal axes, ..... 314 
North Horse valley, . . . .317 
Burns's valley, ..... 318 
Path valley, ..... 318 
Amberson's valley, .... 318 

Structure of Path valley, .... 318 
Fault in Path valley, . . . .319 

Auroral limestone in Path valley, . . . 320 
Composition, ..... 320 
Geographical distribution, .... 320 
Matinal slates in Perry and Franklin counties, . 321 
Composition, . . . . . 321 

Geographical distribution, . . . .321 
Matiuid slate in North Horse valley, . . 321 
Matinal slate in Burns's valley, . . .321 

Matinal slate in Patli valley, . . .321 
Matinal slate N.W. of the fault, . . .322 
Iron ore in the matinal slate along the fault, . 322 
Carrick ore bank, ..... 322 
Mount Pleasant ore bank, . . . 322 

Matinal slate N.W. of Dividing mountain, . 322 
Matinal slate in Amberson's valley, . . 323 
Matinal slate S.E. side of Path valley, . . 323 
Bear valley and its anticlinal axis, . . 323 
Matinal slate in Bear valley, . . . 323 
Auroral and matinal rocks of M'^Connellsburg cove, 323 
Auroral limestone and anticlinal axis, . . 324 

Fault along the N.W. side of the cove, . . 325 
Fault in McConnellsburg cove, . . . 325 

Lowry's knob, ..... 325 
S.W. of Lowry's knob, . . . .326 

Matinal slates of the cove, . . . 326 

Levant sandstones of the Cove mountains, . 326 

Little Scrub ridge, . . . .326 

Dickey's mountain, .... 326 
Cove mountain, .... 327 

Little Cove mountain, .... 327 

CHAPTER II. 

LEVANT AND SUEGENT AND SCALENT EOCKS OF 
PERRY AND FRANKLIN COUNTIES 

Levant series — composition, . . . 328 

Kittatinny mountain, etc., . . . 328 

Surgent and scalent series — composition, . 328 

Surgent slates and ore shales, . . . 328 

Surgent and scalent rocks, . . . 329 

Surgent iron sandstone, . . . 329 

Surgent upper or newer shales, . . 329 

Surgent lower or older shales, . . . 329 

Surgent ore sandstone, .... 329 

Surgent upper or newer ore shale, . . 329 

Surgent red shale, .... 329 

Scalent variegated marls, . . . 329 

Scalent grey marls, .... 329 

Scalent limestone, .... 330 

Levant series, geographical distribution, . . 330 

Levant sandstones, Tuscarora mountain, . . 330 

North-eastern Tuscarora mountain and anticlinal 

axis, ...... 330 



xvi 



TABLE OF CONTENTS. 



Mountain S. E. of Liberty valley, . . 330 

Monoclinal Tuscarora mountain, . . , 331 

Couecoclieagiie mountain, . . . 331 
Levant sandstone in the knobs in the S.W. end of 

Sherman's valley, .... 332 

Round top (anticlinal), .... 332 

The Ri.sing mountain, .... 332 

Levant sandstone. Dividing mountain, . . 332 

Anderson's knob, ..... 332 

Levant sandstones, Bower's mountain, . . 333 

The S.E. division of Bower's mountain, . . 333 

Levant sandstone, Clark knob (of Ambcrson valley), 333 

Levant sandstones of the Kittatinuy mountain, 334 
Spur or angle of Blue mountain south of M'^Clure's 

gap, . . ' . . . . 334 
Spur of the Kittatinuy mountain south of Dublin 

hollow, ...... 334 

Kittatinuy Mountain, S. E. of Shaefter's valley, 335 
Short axis in levant white sandstone between Bower's 
mountain and the Blue mountain, in the south 

west end of Sliaeffer's valley, . . . 33.5 

Levant sandstone in the Kittatinuy or Blue moun- j 

tain N.W. of Roxburg and Strasburg, . 335 i 

Jordan's knob, ..... 33G [ 

Levant sandstones in the mountain S.E. of Bear 

valley, ...... 33G 

Clark's knob, ..... 33G 

Parnell's knob, ..... 336 

Sui'gent series, geographical distribution, . 336 
Surgent slates and shales in Perry and Franklin 

counties, ...... 336 

FossiUferous iron ore, .... 336 

Surgent slates, ore shales, and marls in Perry county 

— range and extent, .... 337 

Fossiliferous ore, Pfout's valley, . . . 337 

Surgent rocks in Racoon valley, . . . 337 
Surgent rocks S.W. of Racoon valley, and in the 

neighbourhood of Ickesburg, . . . 337 

Surgent slates and marls, .... 338 
Siurgent and scalent rocks S.E. of Conecocheague 

mountain, ..... 338 

Surgent rocks on the fifth anticlinal axis, . 339 

Surgent rocks on the sixth anticlinal axis, . 339 

Surgent rocks on the seventh anticlinal axis, . 339 

Buck ridge, fossiliferous ore, . . . 339 

Surgent rocks on the eighth anticlinal axis, . 340 

Surgent rocks on the ninth anticlinal axis, . 340 

Surgent rocks on the tenth anticlinal axis, . 340 

Surgent rocks on the eleventh anticlinal axis, . 341 
Surgent rocks on the twelfth anticlinal axis, or that 

of Bower's mountain, .... 341 
Surgent rocks S.E. of Bower's mountain axis, . 341 
Surgent rocks on the fourteenth anticlinal axis, 342 
Surgent rocks on the fifteenth anticlinal axis, . 342 
Surgent rocks on the seventeenth anticlinal axis, 342 
Surgent rocks in Shaefler's valley, . . 343 
Surgent rocks on the eighteenth anticlinal axis, fossi- 
liferous iron ore, .... 343 
Surgent rocks on the nineteenth anticlinal axis, . 343 
Kennedy's valley, ..... 343 
Surgent slates and shales in the Blue mountain from 

the Susquehanna to Mt^Clure's gap, . . 344 

Surgent slates and shales in South Horse valley, 344 

Horse Valley Proper, .... 344 



Surgent slates in the insulated ridge of the Blue 

mountain S.W. of Strasburg, . . . 344 
Sections, figures Nos. 61, 62, and 63, . . 345 

CHAPTER III. 

SCALENT, PEE-3IEEIDIAN, AND MERIDIAN STRATA IN 
PERRY COUNTY. 



Scalent and pre-meridian limestones — composition, 345 

Scalent and pre-meridian strata— geographical distri- 
tiution, ...... 34f; 

Scalent and pre-meridian limestone in Pfout's valley, 346 

Scalent and pre-meridian limestone in Racoon valley, 346 

The second anticlinal axis, . . . ,340 

Scalent and pre-meridian limestone on the third anti- 
clinal axis, ..... 347 

Scalent and pre-meridian limestone N.E. of the anti- 
clinal axis, . . . . . 347 

Scalent and pre-meridian limestone on the fourth 
anticlinal axis, ..... 347 

Scalent and pre-meridian limestone on the fifth anti- 
clinal axis, . . . . .347 

Scalent and pre-meridian limestone on the sixth anti- 
clinal axis, ..... 347 

Scalent and pre-meridian limestone on the seventh 
anticlinal axis, ..... 347 

Scalent and pre-meridian limestone on the eighth, 
ninth, and tenth anticlinal axes, . . 347 

Scalent and pre-meridian limestone S.E. of Bloom- 
field, ...... 34!) 

Scalent and pre-meridian limestone on the eleventh 
anticlinal axis, . . . . . 349 

Scalent and pre-meridiaa limestone on the twelfth 
and thirteenth anticlinal axes, . . . 349 

Scalent and pre-meridian limestone on the fourteenth 
anticlinal axis, ..... 349 

Scalent and pre-meridian limestone on the fifteenth 
anticlinal axis, ..... 350 

Scalent and pre-meridian limestone on the sixteenth 
anticlinal axis, ..... 350 

Scalent and pre-meridian limestone on the seventeenth 
and eighteenth anticlinal axes, . . . 350 

Scalent and pre-meridian limestone on the nineteenth 
anticlinal axis, . . . . .350 

Scalent and pre-meridian limestone on the N.W. base 
of the Blue mountain, . . . 35t> 

Meridian strata in Perry county. Geographical dis- 
tribution, . . . . .351 

Meridian slates in Perry county, . . 351 

Meridian sandstone in Perry county, . . 35 1 
Iron ore, . . . . .351 

Meridian sandstone S.E. side of Pfout's valley, 351 
Racoon valley, . . . . .351 

Meridian sandstone N.E. of Ickesburg, . 351 

Meridian sandstone on the fourth anticlinal axis, 3.")1 
Meridian sandstone in the ridge three-fourths of a 

mile N.W. of Andersontown, . . . 352 

Meridian sandstone in limestone ridge, . 352 

Meridian sandstone N.W. of the ninth axis, . 352 
Meridian sandstone eighth anticlinal axis, . 352 
Meridian sandstone N.W. of the eighth anticlinal 
axis, ...... 352 

Meridian sandstone S.E. of Bloomfield, . 352 



TABLE OF 



Meridian sandstone opposite Elliotsburg, . 353 
Meridian sandstone saddling the twelfth axis, 353 
Meridian sandstone on the thirteenth anticlinal 

axis, ...... 353 

Meridian sandstone on the fourteenth anticlinal 

axis, ...... 353 

Meridian sandstone S.E. of the fifteenth anticlinal 

axis, ...... 353 

Meridian sandstone in Dick's ridge, anticlinal axis, 353 
Meridian sandstone on the seventeenth anticlinal 

axis, ...... 353 

Meridian sandstone on the eighteenth anticlinal 

axis, ...... 354 

Meridian sandstone on the nmeteenth anticlinal 

axis, ...... 354 

The Warm spring, .... 354 

Meridian sandstone at the base of the Blue moun- 
tain, ...... 354 

CHAPTER IV. 

CADENT AND VEEGENT STRATA IN PEEEY COUNTY. 

Composition, ...... 355 

Cadent older black slate, .... 355 

Cadent shales, ..... 356 

Vergent shales, ..... 356 

Geographical distribution of the cadent and vergent 

rocks in Perry county, .... 356 

Cadent and vergent rocks in Wildcat ridge and 
valley, ...... 357 

Cadent and vergent rocks in Racoon ridge, . 357 
Cadent and vergent rocks between the Juniata and 

Susquehanna above their junction, . , 358 

Half-Fall mountain, .... 358 

Cadent and vergent rocks N.W. of the limestone 
ridge, ...... 358 

Iron ore, Juniata furnace, .... 358 

Cadent and vergent rocks S.E. of the sixth anticlinal 
axis, ...... 359 

Cadent and vergent rocks S.E. of the tenth anticli- 
nal axis, ..... 359 

Dick's ridge, ..... 360 

Mahanoy ridge, ..... 360 

Iron ore along the N.W. base of Mahanoy ridge, . 360 
Cadent and vergent rocks S.E. of Perry furnace, . 360 
Cadent and vergent rocks between the fourteenth 

and fifteenth anticlinal axes, . . . 360 
Cadent and vergent rocks N.W. of Perry furnace, 360 
Cadent lower black slate, .... 360 

Iron ore of the cadent black slate, . . 361 

Cadent and vergent rocks N.W. of the thirteenth 
axis, ...... 361 

Cadent and vergent rocks S.E. of the eighteenth 
anticlinal axis, . . . . .361 

Fishing Creek valley, . . . .361 

Iron ore of the cadent black slate near the Blue 
mountain, ..... 362 

Iron ore at Oak Grove, . ... . 362 

CHAPTER V. 

PONENT EOCKS IN PEEEY COUNTY. 

Composition, ...... 363 

Geographical distribution, .... 363 

Ponent red sandstone in Wildcat valley, . . 363 
VOL. I. 



CONTENTS. 



Ponent red sandstone S.E. of Berry's mountain, . 363 
Ponent red sandstone S.W. of the Juniata, . 363 
Ponent red sandstone N.W. of the Cove mountain, 363 
Ponent red sandstone in Fishing Creek valley, . 364 
Ponent red sandstone S.W. of the ends of Cove moun- 
tain, ...... 364 

CHAPTER VI. 

VESPEETINE CONGLOMEEATE AND UMBRAL EED SHALE 

IN BUFFALO MOUNTAIN. 
Composition, ...... 364 

Geographical distribution, .... 365 

Vespertine conglomerate, Berry's mountain, west of 
the Susquehanna, .... 365 

Cove mountain, ..... 365 

Umbral red shale in Hunter's vaUey, . . 365 
Umbral red shale in the Cove, . . . 365 
Trap dyke, ...... 366 

DIVISION II. 

Third synclinal belt, or Tuscarora valley ; and third 

anticlinal belt, or Shade and Blacklog mountains, 367 
Anticlinal belt, ..... 367 
General description, .... 367 

CHAPTER 1. 
Levant sandstones in the Eastern Shade mountains and 

Blue ridge, ..... 367 

Levant sandstones in the Blue ridge and its anticlinal 

axis, ...... 368 

CHAPTER II. 
Blacklog valley and its anticlinal axis, 369 
Auroral limestone, Blacklog valley, . . 370 
Matinal slates, Blacklog valley, . . . 370 
Levant sandstones in the mountain bounding Black- 
log valley, ..... 370 

The Blacklog mountain, .... 370 

Western Shade mountain, . . . .371 

The Meadow gap, . . . . .371 

Iron ore in Blacklog mountain, . . .371 
Levant sandstones, Shade mountain, S.E. of Blacklog 
valley, . . . . . .371 

Cook's gap, . . . . .371 

Shade gap, ..... 371 

Pott's gap, . . . . .371 

CHAPTER III 
Third, or Tuscarora valley syncUnal, and its several 

belts of the lower and middle levant rocks, . 372 
First anticlinal axis, .... 372 

Second anticlinal axis, .... 373 

Third anticlinal axis, .... 373 

Fourth anticlinal axis, .... 373 

General character of the surgent middle and lower 

groups, ...... 373 

Surgent iron sandstone, .... 373 

Surgent ore sandstone, .... 373 

Surgent slates, ore shales, and marls, . . 373 
Fossiliferous iron ore, .... 374 

Surgent ore shales and marls, S.E. base of Shade 
mountain, E. of the Juniata, . . . 374 

c 



xviii TABLE OF CONTENTS. 



PAGE 

Surgent rocks ; axis of Slenderdale ridge, . 374 

Slenderdale ridge, ..... 375 

Fossiliferous ore, ..... 375 

Slenderdale, ..... 375 

Long Narrows, ..... 37G 

Surgent slates and shales in Lost Creek valley, . 376 
Lost Creek ridge, ..... 376 

Surgent slates and shales, S.W. of the Juniata, above 
Mifflintown, ..... 376 

Hardy's ore-bank, ..... 377 

Forge ridge, ..... 377 

Fossiliferous iron-ore, .... 377 

Jacob's ore-bank, ..... 377 

Licking Creek valley, .... 377 

Surgent slates and shales, S.E. of the Forge ridge, 378 
Surgent slates and shales ; Kurtz valley anticlinal 
axis, ...... 378 

Surgent slates and marls ; Kurtz valley axis, S.W. 
of the Juniata, ..... 378 

Tuscarora valley, ..... 378 

The N.E. portion of Tuscarora valley, . . 379 
The middle division of Tuscarora valley, . . 379 
The S.E. division of Tuscarora valley, . . 379 
The S.W. division of Tuscarora valley, . . 379 
Ridge between the middle and N.W. division of Tus- 
carora valley, ..... 379 

Fossiliferous iron ore, .... 379 

Surgent slates and scalent marls, S.E. of Shade moun- 
tain, 380 
Surgent slates and scalent marls in Pfout's valley, 380 
Surgent slates and scalent marls, S.W. of Thompson- 
town, ...... 380 

Surgent slates and scalent marls, S.E. division of Tus- 
carora valley, . . . . .381 

Surgent slates and scalent marls, N.W. flank of Tus- 
carora movmtain, .... 381 

Surgent slates and scalent marls, S.W. of Waterloo, 

along the Tuscarora mountain, . . 381 

Cove anticlinal axis and its strata, . . 381 
Surgent slates and scalent marls. Cove axis, . 382 

CHAPTER IV. 

SCALENT AND PRE-MEETDIAN LIMESTONES OF THE 
GENERAL TUSCAEOEA SYNCLINAL. 

General characters, ..... 383 
Scalent and pre-meridian limestone, S.E. of Shade 

mountain, ..... 383 
Flintstone ridge, ..... 383 
Scalent and pre-meridian limestone, Slenderdale ridge 

anticlinal axis, ..... 383 
Scalent and pre-meridian limestone, S.E. of Slender- 
dale ridge anticlinal axis, . . . 383 
Scalent and pre-meridian limestone, Blacklog valley 

axis, ...... 384 

Scalent and pre-meridian limestone, S.E. of M'^Allis- 

terstown, ..... 384 
Scalent and pre-meridian limestone, Lost Creek ridge, 384 
Scalent and pre-meridian limestone, Kurtz valley, 384 
■ Scalent and pre-meridian limestone of N.W. side of 

Kurtz valley, ..... 384 
Scalent and pre-meridian limestone, S.E. side of Kurtz 

valley, ...... 385 



Scalent and pre-meridian limestone, S.W. of Perry- 
ville, ...... 385 

Scalent and pre-meridian limestone, S.E. of Shade 
mountain, ..... 385 

Scalent and pre-meridian limestone at the mouth of 
Mahautango creek, .... 385 

Scalent and pre-meridian limestone, N.W. side of 
Pfout's valley, . . . . .385 

Scalent and pre-meridian limestone. Limestone ridge, 386 

Scalent limestone — synclinal axis between the Tus- 
carora mountain and fourth or S.E. anticlinal 
axis, ...... 386 

Scalent and pre-meridian limestones passing Water- 
ford and Waterloo, .... 386 

S.W. of Waterloo, 387 

S.W. of Waterloo gap, . • • .387 

Scalent and pre-meridian limestones N.W. of Cove 
axis, ...... 387 

Pre-meridian chert between Tuscarora mountain 
and Shade and Blacklog mountains, . . 387 



CHAPTER V. 

MERIDIAN SANDSTONE IN THE THIRD OR 
TUSOAEORA SYNCLINAL. 

General characters, ..... 388 

Distribution of the meridian sandstone, . . 388 
Pre-meridian chert, Flintstone ridge, _ . . 388 
Blacklog valley axis, .... 388 

Chert in Kurtz valley, . . . .388 

Chert in the middle division of Tuscarora valley, 388 
Meridian sandstone and chert, S.E. of Shade moun- 
tain, ...... 388 

Chert at the mouth of Mahantango creek, . 389 
Chert in Pfout's valley, . . . .389 

Meridian sandstone and chert limestone ridge, . 389 
Meridian sandstone and chert, N.W. of Waterford 
and Waterloo, ..... 389 

Meridian sandstone, Neely's sawmill, . . 390 



CHAPTER VI. 

CADENT AND VERGENT ROCKS OF THE THIRD OE 
TUSCAEOEA SYNCLINAL. 

General characters, ..... 390 
Distribiition of the cadent and vergent rocks, . 391 
Cadent and vergent rocks, S. of Selinsgrove, . 391 
Cadent and vergent rocks, N. of JI'^Key's Half-Falls, 391 
Cadent and vergent rocks, S.E. of the mouth of 

Mahantango creek, . . • .391 
Cadent and vergent rocks between Pfout's valley 

and Flintstone ridge, .... 392 
Cadent and vergent rocks, Kurtz valley anticlinal 

axis, 392 
Turkey ridge, ..... 392 
Cadent and vergent rocks, S.W. of the Juniata, . 393 
S.W. of Perryville, . • • .393 

Cadent and vergent rocks, the S.W. extremity of 

Tuscarora valley and Little Aughwick valley, 393 
Iron ore, !594 
Ponent red sandstone on the Susquehanna, . 395 



TABLE OF CONTENTS. xix 



DIVISION III. 

FOtTRTH SYNCLINAL BELT, OR LEWISTOWN VALLEY 
AND ITS BRANCHES, FROM THE SUSQUEHANNA 
SOUTH-WESTWARD. 



Preliminary remarks, .... 396 

Anticlinal axes, ..... 396 

Lewistown valley, .... 396 

CHAPTER I. 

Character of the several formations in the belt, . 397 

Surgent series, ..... 397 

Surgent ore shales, .... 398 

Scalent marls, ..... 398 

Scalent limestone, .... 398 

Pre-mericlian series, .... 399 

Prc-meridian sandy shale, . . . 399 

Meridian sandstone, . . . ■ . 399 

Cadent and vergent series, . . . . 399 

Cadent older black slate, . . . 399 

The iron ore, ..... 400 

Ponent red sandstone, .... 400 
Lewistown valley, . . . .401 

CHAPTER II. 

Topographical features of the several strata, . 401 

Topography of the meridian strata, . . 401 

The pre-meridian limestone and meridian sandstone, 402 

Hills of the cadent, vergent, and ponent rocks, . 402 

CHAPTER III. 

Flexures or axes in Lewistown valley, . . 403 
Anticlinal axis of Longstown ridge and Jack's 

mountain, ..... 403 

Synclinal trough of Blue hill, . . . 403 

Anticlinal axis of Shade mountain, . . 403 

Axes of the district between the Susquehanna and 

Lewistown, ..... 404 

Axis in Moser's valley, .... 404 

Anticlinal axes, <tc. in Adamsburg valley, and valley 

of Middle creek, .... 405 

Anticlinal axis S. of Middleburg, . . . 405 

Knolls of pre-meridian limestone near Beavertown, 405 

Lewistown valley, near Kishacoquillas creek, . 406 

Anticlinal axes on Kishacoquillas creek, . 407 

Synclinal troughs on Kishacoquillas creek, . 407 

Topography of Forge ridge, . . . 408 

General synclinal structure of Dry vaUey, . 409 

Anticlinal flexure in Dry valley, . . . 409 

CHAPTER IV. 

Iron ores, ...... 410 

Iron ores in the meridian sandstone and cadent 

black slate, ..... 410 

Iron ores in the scalent and pre-meridian lime- 
stones, . . . . .410 

Iron ores in the surgent rocks, . . . 410 

Lower ore, ..... 410 

Block ore, ..... 410 

FossUiferous ore, .... 4.^0 



CHAPTER V. 



Fourth synclinal belt — from Lewistown to the Mary- 
land line, . . . . .411 
Range of the several formations in the Lewistown 

valle.y, from Lewistown to Maryland, . 412 

Surgent series— surgent slates and marls, N.W. 
of Lewistown, and along the flank and base of 
Jack's mountain to its termination, . . 412 
Fossiliferous ore and hard belt, . . 412 

Surgent slates and scalent marls S.E. of Lewis- 
town and Waynesburg, along the Blue ridge, 413 
Fossiliferous ore and ore sandstone, . . 413 
Germany valley, .... 414 

Surgent slates and scalent marls along the Black- 
log mountain, ..... 414 
Sulphate of barytes, .... 414 

PIGEON COVE. 

Surgent marls, . . . . .414 

Little Scrub ridge, .... 415 

Surgent slates and scalent marls, . . 415 

Dickey's mountain, .... 415 

Surgent slates and shales, and scalent marls, Little 
Cove, ...... 415 

Fossiliferous ore of Little Cove, . . 416 

CHAPTER VL 

Scalent and pre-meridian limestones in Lewistown 
valley, . . . . . . 416 

Geographical range, .... 416 

Limestones near the second anticlinal axis, . 417 
Scalent and pre-meridian limestones. Hill valley, 417 
Scalent and pre-meridian limestones, third anticlinal 
axis, ...... 417 

Scalent and pre-meridian limestones, fourth anticli- 
nal axis, ...... 417 

Pre-meridian limestone. Prater's ridge, . . 418 
Scalent and pre-meridian limestone in Negro valley 
and Blue ridge, . . . . .419 

South-east side of Great Aughwick valley, . 419 
Scalent and pre-nieridian limestone, Pigeon Cove, 419 
Scalent and pre-meridian limestone, Little Scrub 
ridge, . . . . . . 419 

Scalent and pre-meridian limestone. Little Cove, . 419 

CHAPTER VII. 

Meridian sandstone of the belt, . . . 420 
Meridian sandstone in the synclinal trough N. of the 
first anticlinal axis, .... 420 

Meridian sandstone axis of first and second anticlinal 
axes, ...... 420 

Meridian sandstone, synclinal trough between the 

second and fourth anticlinal axes, . . 420 
Long Hollow ridge, . . . .421 

Meridian sandstone between the fourth and fifth anti- 
clinal axes, ..... 422 

Meridian sandstone between the fifth and sixth anti- 
clinal axes, ..... 422 

Meridian sandstone. Prater's ridge, . . 422 
Meridian sandstone S.E. of the sixth anticlinal axis, 423 
Meridian sandstone S.E. of Blue ridge, . . 423 

Meridian sandstone in Great Aughwick valley, . 423 
Meridian sandstone in Pigeon Cove, . . 423 



TABLE OF CONTENTS. 



Meridian sandstone, Little Scrub ridge, . . 424 
Dickey's mountain, . . . . 424 

Meridian sandstone in Little Cove, . • . 424 

CHAPTER VIIL 

Cadent and vergent strata in the belt, . . 424 
Cadent lower black slate — synclinal trough between 

first anticlinal axis and Jack's mountain, . 425 
Synclinal trough of the first and second anticlinal 

axes, ...... 425 

Cadent lower black slate — synclinal trough of the 

second and fourth anticlinal axes, . . 425 

Belt south-cast of the third anticlinal axis, . . 425 
Cadent lower black slate between the fourth and 



seventh anticlinal axes, . . . 425 

Trough between the fifth and sixth anticlinal axes, 426 
Cadent and vergent rocks in Juniata or Green Briar 

valley, ...... 426 

Iron ore, Morrison's ore-bank, . . . 426 
Cadent black slate — synclinal trough between the 

sixth anticlinal axis and Blue ridge, . . 426 

Synclinal basin, which is the prolongation south- 
west of that of Negro valley, . . . 427 



The ponent strata from the higli land south-west of 
the junction of Three Spring and Great Aughwick 
creeks, and between them, . . . 427 
Cadent and vergent rocks along the S.E. side of the 
Great Aughwick valley, . . . 427 

Cadent and vergent rocks — synclinal trough anticlinal 
axis of Blacklog valley and M'^Connellsburg Cove, 428 

Cadent and vergent rocks — prolongation of the anticli- 
nal axis of Blacklog valley, . . . 428 

Belt north-west of Pigeon Cove, . . . 428 

Belt south-east of Pigeon Cove, . . . 428 

Cadent and vergent rocks — belt north-west of M'^Con- 
nellsburg Cove, ..... 428 

Little Cove (Franklin county), . . . 429 

CHAPTER IX. 

rONENT AND VESPERTINE ROCKS OP THE BELT. 

Ponent red sandstone of Great Aughwick valley, 429 
Ponent red rocks, synclinal basin between the axes of 
Blacklog valley and Pigeon Cove on the north-west, 
and M'^Connellsburg Cove on the south-east, 430 
Big Scrub ridge, ..... 430 
Vespertine conglomerate, Big Scrub ridge, . . 430 
Umbral red shale, . , . . .431 

CHAPTER X. 

IRON ORES OF THE DISTRICT. 

Surgent fossUiferous ore, Huntingdon and Mifflin 

counties, . . . . . .431 

Fossdiferous ore of Hope furnace, Mifflin county, 432 
Worral's ore bank, .... 432 

Surgent cellular ore of Hanover furnace, . . 432 

Iron ore of the meridian sandstone and slate Chest- 
nut ridge, Huntingdon county, . . . 432 

Iron ore of the cadent lower black slate, . . 432 
Brookland furnace-bank, .... 432 
Walter's bank, ..... 433 
Cresswell's ore-bank, . . . 433 



Mevey's ore-bank, ..... 433 
Ore banks of Chester furnace, . . . 433 

BOOK IV. 

SIXTH OR UPPER JUNIATA DISTRICT, BEING THE 
NORTH-WESTERN HALF OF THE APPALACHIAN CHAIN 
BETWEEN THE SUSQUEHANNA AND MARYLAND. 



Boundaries, ..... 434 
DIVISION L 

FIRST BELT OF THE SIXTH DISTRICT, MONTOUR RIDGE, 
BUFFALO VALLEY, MUNCY HILLS, ETC. 

Subdivisions and boundaries, . . . 434 
CHAPTER L 

Character of the strata ; their local type, . . 435 

Levant, surgent, and scalent series, . . 435 

Section of the surgent strata near Danville, descend- 
ing, 435 
Surgent lower slate, Montour ridge, . . 436 
Surgent iron sandstone, .... 436 
Surgent upper strata, .... 436 
Surgent lower calcareous shale, . . . 436 
Surgent-ore sandstone, .... 437 
Montour ridge, ..... 437 
Surgent upper calcareous sliale, . . . 437 
Surgent red shale or red marl, . . . 437 
Scalent variegated marls, .... 437 
Scalent grey marls, .... 437 
Scalent limestone, ..... 438 

Pre-meridian and meridian series, . . . 438 

Pre-meridian limestone, .... 438 

Meridian slates, ..... 438 

Meridian sandstone, .... 439 

Cadent and vergent series, . . . 439 

Strata of the Muucy hills (see Section), . . 439 

Ponent series, ..... 440 

CHAPTER IL 

Anticlinal belt of Montour ridge, . . . 440 
Structure and contents of Montour ridge, . . 440 
Montour ridge at DanviUe, Hemlock creek, and Fish- 
ing creek, ..... 441 

Surgent upper calcareous shales at Danville, . 442 

Iron ores at Danville, .... 443 

Montour ridge, between the Mahoning and Hemlock 

creeks, ...... 444 

Danville, ...... 445 

Montour ridge, east of Hemlock creek, . . 446 

Fishing creek, ..... 447 

Amount of iron ore in Jlontour ridge, . . 448 
Iron ores of the west or Mahoning creek di-\ision of 

Montour's ridge, .... 449 

Tabulated statement of the total quantity of iron ore 

ill Montour's ritlge in an attainable position, . 450 

Concluding remarks, .... 450 

CHAPTER III 

Scalent, pre-meridian, meridian, cadent, and vergent 

rocks of the anticlinal belt of Montour ridge, . 451 



TAELE OF CONTENTS. 



xxi 



452 



452 



Details of tlie composition and contents of the meridian, 
pre-meridian, and scalent strata, S.W. of Blooms- 
burg, in tabular form, . . . .451 

Cadent and vergent rocks of the anticlinal belt of the 
north branch of Susquehanna, . 

The synclinal belt of Mahauoy ridge and Buffalo 
valley, ...... 

DIVISION II. 

Second belt of the fifth district or anticlinal north of 
Shickshinny mountain, .... 453 

CHAPTER I. 

The anticlinal belt of Upper Fishing creek, . . 453 

CHAPTER II. 

The synclinal belt of Mimcy hills, . . . 454 

Whitedeer Hole valley, .... 455 

Surgent red shale, .... 455 

Pre-meridian limestone, .... 455 

Cadent black slate, .... 455 

Surgent rocks of "\^Tiitedeer Hole valley, . . 455 
Pre-meridian and scalent limestones of Whitedeer 

Hole valley, ..... 456 

Meridian sandstone, .... 456 

Cadent dark olive slate, .... 456 

CHAPTER III. 

Buffalo valley, ..... 456 

Levant white sandstone in Buffalo valley, . 458 

Surgent shales and scalent marls in Buffalo valley, 458 

Surgent calcareous shale, or fossUiferous ore shale, 458 

Scalent limestones, .... 459 

Buffalo valley. Lead ore, .... 460 

Cadent black slate, .... 460 

DIVISION III. 

THIRD BELT OF THE SIXTH DISTRICT, OE THE COUNTRY 
EMBRACED BETWEEN JACK's MOUNTAIN AND SIDE- 
LING HILL ON THE SOUTH-EAST, AND BALD EAGLE, 
DUNNING'S and wills' MOUNTAINS ON THE NORTH- 
WEST. 

CHAPTER I. 

General structural features of the district, . . 461 
Anticlinal axis of Montour's ridge, . . 462 

Anticlinal and synclinal axes of Kishacoquillas and 
the other limestone valleys of Union, Mifflin, 
Centre, Blair, and Bedford counties, . . 462 
Kishacoquillas valley, .... 463 
Anticlinal axis of Moser's and Swartzel's valleys, 463 
Anticlinal axis of the main spur of Jack's mountain, 

or main axis of Orr's valley, . . . 463 

Subordinate axis of Orr's valley and Perry ville, . 464 
Anticlinal axis of Buffalo and Christman's valleys, 464 
Anticlinal axis of Jack's mountain of the Juniata, 464 
Anticlinal axis of Po valley, . . .464 

Anticlinal axis of Penn's Narrows, . . 465 

Anticlinal axis of Penn's valley, . . . 465 

Anticlinal axis of Brush valley, . . . 466 



PAGE 

Anticlinal axis of Little valley or AVTiitdeer creek, 466 
Anticlinal axis of Sugar valley, . . . 466 

Main anticlinal of Nittany valley, . . . 467 

Anticlinal axis of the S.E. side of Nittany vaUey, 467 
Flexures S.W. of the Little Juniata, . . 468 

Anticlinal axis of Canoe valley, . . . 468 
Anticlinal axis of the W. side of Morrison's Cove, 468 
Anticlinal axis of Friend's Cove, . . . 469 
Anticlinal axis of Milliken's Cove and Wills' moun- 
tain, ...... 469 

CHAPTER IL 

Character of the formations, .... 469 
Auroral and matinal rocks, . . . 469 

Auroral magnesian limestone, . . . 470 
Auroral limestone, Nittany valley. Tabulated details, 471 
Matinal limestone (Trenton limestone of New York), 471 
Matinal black slate (Utica slate), . . .472 
Matinal shales (Hudson river slate), . . 472 
Levant rocks, ..... 472 
Levant grey sandstone, .... 472 
Levant red sandstone, .... 473 
Levant white sandstone, .... 473 

Causes of the peculiar structure of the district em- 
braced between Jack's and Bald Eagle moun- 
tains, ...... 



CHAPTER III. 

Kishacoquillas valley. 
Topographical description, . 
Flexures of the strata. 

Anticlinal axis, Swartzel's valley. 

Anticlinal axis of Orr's valley, 

Baird's and Stewart's knobs. 

Anticlinal axes of Perry ville. 

Anticlinal axis of Jack's mountain. 

Fault in Stone mountain, . 

Jack's mountain, . 
Rocks of Kishacoquillas valley. 

Auroral limestone, . 

Matinal limestone (Trenton limestone), 

Matinal shale. 
Iron ores of Kishacoquillas valley. 

Surface ores, 

Davis' bank. 

Holiday's ore bank, 

Old ore bank of Hall and Rawle, 

Brookland furnace ore bank, 

M'^Connellsburg Cove, 

Hanover ore bank, . 

Ice cave, 

Matinal black slate, 
Sinking Spring gap, 
Christman's valley, 

CHAPTER IV. 

Region of the Seven mountains. 

Section across the Seven mountains by the turn])ike 
road, .... 
The Seven mountains, 5 miles east of the turnpike, 
The Seven mountains, from Hartman's northward. 



474 



475 
475 
475 
475 
475 
476 
476 
477 
477 
477 
478 
478 
478 
478 
479 
479 
479 
479 
479 
479 
479 
479 
479 
480 
480 
480 



480 

481 
481 
481 



TABLE or 



CONTENTS. 



Contours of the ridges from the summit of Big 

mountain, ..... 482 

Anticlinal spurs and axes, .... 482 

Barrier of the auroral and matinal region, . 483 

CHAPTER V. 

Region of the Buifalo, Nittany, and Bald Eagle moun- 
tains, ...... 483 

Short mountain, ..... 483 

Brush mountain, ..... 483 

Terrace mountain, seen in profile (see fig. 88), . 484 
Brush mountain from the north side of Brush valley 

(see fig. 89), ..... 484 

Plateau of Nittany mountain, . . . 484 

Pheasant valley, ..... 485 

Mountain spurs of Union county, . . . 485 

Little valley, ..... 486 

Nittany mountain, ..... 480 

Nittany mountain, &c., as seen from Bald Eagle 

mountain (see fig. 90), . . . 487 

Big mountain, ..... 487 

Sugar valley, ..... 487 

Nittany mountain, opposite the east end of Nittany 

valley (see fig. 91), . . . . 488 

Anticlinal belt between Nittany and Nippenose val- 
leys, . . . . .488 

Nittany valley anticlinal axis (see fig. 92), . 488 

Gaps, Anti's gap, ..... 489 

Ravines in the south barrier of Nippenose valley, 489 

CHAPTER VI. 

Nippenose, or the Oval limestone valley, . . 490 

Fossils in the matinal black slate ia Anti's gap, . 490 

CHAPTER VII. 
Sugar valley, . . . . . .491 

CHAPTER VIII. 

Brush valley, ...... 492 

Matinal slate, ..... 492 

Brush valley, ..... 493 

CHAPTER IX. 

Penn's valley, ...... 493 

George's valley, ..... 493 

Anticlinal axis of Brush valley, . . . 494 

CHAPTER X. 

Section opposite Millhall gap, . . . 495 

Section at Washington gap, .... 496 

Section near Jacksonville, .... 496 

Section at Jacksonville, .... 496 

Section at Heclar furnace, .... 497 

Section of the valley at the Bellefonte gap, . . 497 
Section across the whole valley half a mile west of 

Nittany mountain, .... 498 

CHAPTER XI. 

The iron ore beds of the Nittany valley, . 499 



CHAPTER XII. 




JN ittany valley — (continued), .... 


PAGE 

500 


Jl. lie Xicll 1 CllOj . • . * . 


OUi 


The Nittany anticlinal continued, westward, 


r; AO 
oOz 


Section passing Birminghanij 


503 


f aULl, ...... 


504 


CHAPTER XIII. 




Canoe valley j or Nittany valley— (continued), 


504 


Subordinate axis of Tussey mountain, 


504 


The matinal rocks, ..... 


505 


The Barrens, ..... 


505 


Morrison's Cove, ..... 


506 


CHAPTER XIV. 




Morrison's Cove or Canoe valley prolonged, 


507 


Cunning's mountain and High Barrens, . 


507 


CHAPTER XV. 




ouuKe oprmg vauey anu rrienus L^ove, 


oOo 


Axes, ...... 


508 


Cove creek, ...... 


508 


CHAPTER XVI. 




Bean's Cove, ...... 


509 


Anticlinal axes, ..... 


509 


Martin's hill, Bean's Cove, 


510 


CHAPTER XVII. 




wills' mountain and milliken's cove. 




TUT '11 ' J. • 

Wills mountam, ..... 


510 


Milliken's Cove, ..... 


511 


DIVISION IV. 




FriTTRTTT 'RTT T AT? TTTF c:t"VT1T "HT^iTTJTPT OTf SiTn^CV 








4 "XT T\ 'O'D^ A mi^T> Ti.f/'^TT'WFll A TXT 

Ar^D xSKOAD lOF MOUNIAIN. 




CHArilsK 1. 




Stone vaUey, ..... 


512 


Synclinal trough of Milliken's knob in Kishacoquillas 




valley, ...... 


513 


Anticlinal axis of Broad Top mountain, . 


512 


Anticlinal axis of Stone creek knob, 


513 


Anticlinal axes of the spurs of Bear Meadow moun- 




tain, ...... 


513 


Anticlinal axes of the spurs of Tussey's mountain, 


514 


Warrior ridge, ..... 


515 


Levant white sandstone of Tussey's, Stone, and other 




mountains, ..... 


.515 


Surgent slates and ore-shales at the base of the moun- 




tains, ...... 


515 


Tussey's mountain, .... 


515 


Ores in Stone valley, .... 


516 


Scalent marls of Stone valley, 


517 


Scalent limestone of Stone valley. 


517 


Iron ore, ...... 


518 


Meridian sandstone, .... 


518 



TABLE OP CONTENTS. 



xxiii 



Warrior ridge at the Pulpit rocks, . . 519 

Pulpit rocks, ..... 520 

Cadent series iu Stone valley, . . . 520 

Vergent rocks iu Stone valley, . . . 520 
Ponent rocks in Stone valley, . . .521 

CHAPTER II. 

Hare valley, . . . . . .521 

Topography, . . . . .521 

Standerfer's knob and side view of Jack's mountain, 522 

Fossiliferous iron ore, .... 522 

CHAPTER III. 

Woodcock vaUey, ..... 522 

Woodcock valley at M'^Connellsto'WTi, . . 523 

Levant series — Tussey mountain, &c., . . 523 

Surgent iron ore, ..... 523 

Woodcock valley at Trough Creek gap, . 524 
Pre-meridian and meridian series. Warrior ridge, 

&c., ...... 525 

Black Oak ridge, ..... 525 

Iron ore connected with the lower layers of the scal- 

ent limestone, ..... 526 

Cadent, vergent, and ponent rocks — Allegrippus 

ridge. Clear ridge, (fee, . . . 526 

Iron ore, ...... 527 

CHAPTER IV. 

Tubmill harbour and the country south of it, . 527 

Terrace mountain, ..... 527 

CHAPTER V. 

The Broad Top region, . . . .628 

Topography, ..... 528 

Vespertine strata, ..... 528 

Iron ores, ...... 529 

TJmbral limestone distribution, . . . 530 

Umbral rocks in the flank of Broad Top mountain, 531 
Trough Creek valley, . . . .532 

Vespertine sandstone, .... 533 



DIVISION V. 

OF THE FIFTH BELT OF THE SIXTH DISTRICT, OE THAT 
BETWEEN TEE BALD EAGLE AND ALLEGHANY 
MOUNTAINS. 



Preliminary remarks, .... 534 

CHAPTER I. 

Of the character of the surgent, scalent, pre-meridian, 
meridian, cadent, vergent, and ponent rocks at 
the base of the Alleghany mountain, . . 535 
Surgent, scalent, pre-meridian, and meridian series, 535 
Strata exposed on the west branch of Susquehanna 
river, between Jersey shore and Muncy (also at 
Milton), . ■ . . . . .535 

Tabulated details, ..... 536 
Surgent slates, ..... 536 
Howard furnace ores, .... 537 



Surgent ore shales, .... 537 

Surgent lower ore shale, . . . 537 

Surgent upper ore shale, . . . .537 

Surgent and scalent marls, . . . 638 

Surgent red shale, .... 638 

Scalent variegated marls, . . . 538 

Scalent grey marls, .... 538 

Scalent limestone. Bald Eagle valley, . . 639 

Thickness, ..... 539 

Pre-meridian series, .... 539 

Pre-meridian limestone, .... 539 

Thickness, ..... 539 

Meridian series, ..... 539 

Meridian slates — thickness, . . . 539 

Meridian sandstone, .... 539 

Cadent and vergent series at the foot of Alleghany 

mountain, ..... 540 

Cadent lower black slate, . . . 540 

Cadent olive shale, .... 540 

Thickness, ..... 640 

Cadent upper black slate, . . . 540 

Thickness, ..... 540 

Vergent flags, ..... 540 

Thickness, ..... 641 
Vergent shales, . . . . .641 

Thickness, ..... 541 

Iron ore, ...... 541 

Ponent series, Bald Eagle valley, . . . 541 

Thickness, ..... 641 

Strata near Cumberland on the Potomac, . 641 

CHAPTER II. 

Levant, surgent, scalent, pre-meridian, and meridian 

series, ...... 542 

Along the valleys of the west branch and Bald Eagle 

from Muncy to Milesburg, . . . 642 

Surgent red shales, .... 542 
Surgent and scalent rocks iu Bald Eagle valley 

— tabulated details, .... 543 

Pine creek near Jersey shore, . . . 644 

Description of the strata, . . . 644 
Bald Eagle mountain ■ — Sketch showing difl'erent 

vegetation upon different rocks, . . 545 

Bald Eagle creek valley, section at Eagle furnace, 546 

Strata N.W. of Millhall— details, . . 646 

Meridian rocks iu Bald Eagle valley, . . 547 

CHAPTER III. 

Cadent and vergent rocks from Muncy to Milesburg, 548 

Bald Eagle valley, ..... 549 

Rocks on Larry's creek near the Susquehanna river, 550 
Short mountain synclinal, and anticlinal of Canoe 

Run, Vt'ith vergent iron-ore, . . . 550 

Vergent rocks and iron-ore in Bald Eagle vaUey, . 560 

CHAPTER IV. 

Levant, surgent, scalent, cadent, and vergent rocks, 552 
Little Bald Eagle valley, from Milesburg to Holi- 

daysburg, ..... 552 

Lock and Canoe mountains, . . . 653 

Bald Eagle mountain N.E. of Hannah furnace, 553 
Profiles of the crest and terrace of Bald Eagle 

mountain, .... 553 



xxiv 



TABLE or CONTENTS. 



PAGE 

Oblique meeting of Anticlinals of Lock and Canoe 
mountains, ..... r)54 

Scaleut, grey marls, and limestones on the Juniata 
above Bell's forge, .... 554 

Section of surgent, pre-meridian, and meridian rocks 
above Bell's forge on the Juniata, . . 554 

CHAPTER V. 

Levant and surgent series, Frankstown Cove and Dun- 

ning's mountain, S.W. to Buckstowu, . . 555 
Frankstown Cove, .... 555 

Dunuing's mountain, .... 556 
Displaced summits of Canoe mountain near the 

Juniata, ...... 556 

Section of the strata near Canoe movmtain, . 556 

Lock mountain, .... 557 

View of Frankstown knob (anticlinal) from the top 

of Blue knob in the west, . . . 557 

CHAPTER VL 

Pre-meridean, meridian, cadent, vergent, and ponent 
strata from Hollidaysburg S. W. to Bucks- 
town, &c., ..... 558 
Four miles S.W. of M^Kee's gap, . . . ' 558 
Anticlinal of Pine ridge, with scalent and pre-meri- 
dian limestone and chert, . . . 558 
Flexures and blocks of meridian sandstone N.E. of 

Buckstown, ..... 558 

Buckstown, ..... 558 

Dutch Corner, . . ■ . . . 559 

Cadent and vergent series S.W. of Hollidaysburg, 559 

Ponent series S.W. of Hollidaysburg, . . 559 

CHAPTER VII. 

Surgent series cast of Buckstown (Dutch Corner, &c.), 560 
Details of a section made at the end of Buckstown 

mountain, ..... 560 
Scalent and surgent strata opposite the end of 
Buckstown mountain, . . .561 

CHAPTER VIII. 

Cadent and vergent series S. and E. of Buckstown in 
Dutch Corner, and along the line of Chestnut 
ridge in Blair county, .... 561 
End of Lime ridge, near Bedford, . . 562 

Dutch Corner, ..... 562 

CHAPTER IX. 

Cadent, vergent, and ponent strata S.W. of Buckstown, 563 
Bob's creek at Buckstown, . . . 563 

Dunning's creek, ..... 664 
Strata S.W. of Buckstown, . . . 565 

Bedford and Greensb^lrg turnpike, . . 565 

Ponent series W. and S.W. of Chestnut ridge axis, 565 
Form of the escarpment of the Alleghanny mountain, 565 



CHAPTER X. 

COUNTRY SOUTH OF THE RAYSTOWN BRANCH OF 
JUNIATA IN THE FOURTH BELT OF THE SIXTH 
DISTRICT. 



Bedford synclinal basin (Cumberland valley), from 
Bedford to the Maryland State Line — Surgent, 
pre-meridian, meridian, cadent, and vergent 

series, ...... 565 

Surgent series, ..... 565 

Cumberland valley, .... 566 

Outcrop of the fossOiferous iron ore and pre-meridian 

limestone, ..... 566 

Hollidaysburg turnpike, .... 566 

Surgent rocks, ..... 567 

Deddiug's creek and one mile south, . . 567 
Pre-meridian, scalent, surgent, and levant strata, as 

exhibited at the Maryland line, . . 567 

Cadent and vergent series, . . . 568 
Gorge through the Bedford Springs, exhibition of 

the strata, ..... 568 

Cadent and vergent rocks, . . . 569 
One mile S.W. of Bedford, . . .569 

Cumberland valley at the Maryland line, . 570 

CHAPTER XI. 

Country W. of Buffalo mountain, . . . 570 

Surgent series, ..... 570 

Pre-meridian limestone, .... 571 

Cadent black slate, .... 572 

Cladding's run, ..... 572 

Cadent and vergent rocks, . . . 573 

Ponent series, ..... 574 

Savage and WiUs' mountains, . . . 574 

Jenning's run, ..... 575 

BOOK VII. 

Seventh or north-western district, . . . 576 

CHAPTER I. 

Of the Geology of Erie and Crawford, and the northern 

half of Warren counties, . . . 576 

Topographical features, .... 576 

Formations, ..... 577 

Local composition, ..... 578 

Erie and Crawford counties, . . . 578 

Composition of the formations, . . . 579 

Thickness of the formations, . . . 580 

Features of deposition, .... 581 

Concretionary structure, &c. . . . 581 

Thickness of the strata, .... 581 

CHAPTER II. 

Economical and other details, . . . 582 

Building stone, ..... 583 



ILLUSTRATIONS 

IN THE 

FIRST VOLUME, 



SKETCHES OF SCENERY, &Q. 



FRONTISPIECE— PULPIT ROCKS, WARRIOR RIDGE, HUNTINGDON COUNTY. 

GNEISS ROCKS NEAR THE MOUTH OF THE WISSAHICKON, . . . To face page 5 

KITTATINNY MOUNTAIN FROM LEHIGH SUMMIT MINES, . . . .... 9 

WEST BRANCH OF SUSQUEHANNA AND BALD EAGLE MOUNTAIN FROM FAIR VIEW INN, ... 11 

HUNTINGDON AND JACK'S MOUNTAIN FROM WARRIOR RIDGE, . . . ... 13 

PART OF SUMMIT MINE OF LEHIGH COMPANY, . . . . . .... 25 

PASS OF THE LEHIGH AT MAUCH CHUNK, . . . . . .... 29 

COUNTRY AROUND CANONSBURG, WASHINGTON COUNTY, . . . . ... 37 

WEST BRANCH OF THE SUSQUEHANNA FROM THE MUNCY HILLS, . . . ... 51 

SKETCHES OF QUARRIES ON THE SCHUYLKILL, SHOWING METAMORPHISM, . ... 213 

SECOND MOUNTAIN-GAP, SUSQUEHANNA RIVER, . . . . . .... 365 

MILLIKEN'S COVE IN WILLS' MOUNTAIN, FROM DRY RIDGE; ALSO VALLEY OF 

JUNIATA RIVER, LEWISTOWN, . . . . . . . .... 369 

BLUE HILL, NORTHUMBERLAND, PENNSYLVANIA, . . . . . . ...397 

KISHACOQUILLAS VALLEY FROM BAIRD'S KNOB, ALSO BLACKLOG AND SHADE MOUN- 
TAINS FROM MIFFLINTOWN, . . . . . . .... 462 

SPURS OF JACK'S MOUNTAIN, EAST END OF KISHACOQUILLAS VALLEY, . . ... 476 

LEHIGH WATER-GAP FROM STONE RIDGE, . . . . . . .... 489 

NATURAL BRIDGE ON ARCH SPRING, . . . . . . . .... 503 

INDIAN CHIEF ROCK, NEAR WILLIAMSBURG, JUNIATA RIVER, . . . ... 506 

STONE OR ROCKY RIDGE NEAR JACK'S NARROWS, JUNIATA RIVER, . . ... 519 

STONE RIDGE NEAR JACK'S NARROWS; ROCKS MUCH FISSURED, . , . ... 520 

PINE CREEK GAP, LYCOMING COUNTY, . . . . . . .... 534 

BELLEFONTE, CENTRE COUNTY, . . . . . . . . .... 546 

END OF CANOE MOUNTAIN IN SINKING VALLEY, . . . . . . ...555 

EASTERN FRONT OF THE ALLEGHANY MOUNTAIN, FROM NEAR HOLLIDAYSBURG, ... 559 

VOL. I. d 



ERE ATA. 



Page 174, line 32, for Fig. 25, read 2Za,page 181. 

„ 216, line 15, for Marble Hill, read Blarhle Hall. 

„ 383, line 21, for Pre-Meridian Sandstone, read Meridian Sandstone. 

„ 476, line 1, for Baird's, read Betty's. 

„ 505, last line, for Williamsport, read Williamslmrg. 

„ 543, line 11, for Levant formations, read Surgent formations. 

„ 554, line 19, for Levant ore calcareous shales, read Surgent, <fcc. 

„ 554, line 22, for Surgent shales and marls, read Scalent, Sc. 

„ 559, line 34, for Black Knob, read Blue Knob. 



GEOLOGY OF PENNSYLVANIA. 



INTRODUCTION. 

PHYSICAL GEOGKAPHY OF PENNSYLVANIA. 

A TRUE notion of the Geology of a region so complex as Pennsylvania cannot be easily acquired 
without a preliminary survey of its Physical Geography. The external relief, or surface- 
modelling of a country, is indeed but the expression of its internal rocky structure, as moulded 
by the erosive action of moving water and the slow chemical influences of the atmosphere. The 
contour of the ground is the sculpture which guides to the anatomy within ; and it is as needful 
to note the slopes, projections, and wavy outlines of the surface, while studying the mineral 
masses beneath it, as it is for the anatomist to employ the perceptions of the artist. 

Few districts of the globe — certainly no portions of the wide Appalachian area — disclose this 
connection between the external physical features of the land and the characters and j^ositions 
of the strata, more plainly than the State of Pennsylvania. I shall therefore preface my account 
of its Geology by a sketch of its external features. While describing these, it will be expedient 
to offer a brief sketch of the hydrography or river-drainage of the region, and to introduce some 
general statements respecting its climate, especially the conditions of temperature and rain, which 
control so entirely the irrigation of the surface. But first of all it is essential that I define the 
Boundaries and Position of the State. 

BOUNDARIES AND AREA. 

Pennsylvania is bounded on the N. by the east and west line which separates it from New 
York and by Lake Erie ; on the E. by the Delaware Kiver, dividing it from New Y'ork aud 
New Jersey ; on the S. by the States of Delaware, Maryland, and Virginia ; and on the W, 
by a part of Virginia and Ohio. The length of the State in an E. and W. direction is about 
310 miles, and its breadth 160 miles. Its shape is nearly that of a parallelogram. It lies 

A 



WATER-SHED AND SLOPES. 



between latitudes 39° 42' and 42° 15' N., and between the meridians 2° 18' E., and 3° 32' 
W. from Washington. The surface of the State embraces very nearly 44,400 square miles, or 
28,416,000 acres. The central and northern parts are mountainous, but include many ample 
valleys of great fertility and beauty, while the south-eastern and western portions possess a more 
gently undulating surface. The height above the sea of the loftiest ridges and table-lands 
scarcely exceeds 2800 feet, and the average elevation of the whole surface is probably about 
600 feet. 

POSITION OP THE STATE. 

The position of this State in relation to the great slopes, and therefore to the river systems of 
the country, is most interesting and important. An inspection of the geological map will 
show that, while the territory of the Commonwealth touches the Atlantic tide-water plain at its 
south-eastern border, and derives therefrom the invaluable privilege of a free outlet to the ocean, 
it embraces the Atlantic Slope, the whole breadth of the Appalachian Mountain-chain, and nearly 
all the upper or north-eastern extremity of the great and fertile basin of the Ohio Eiver. It has 
the further advantage of touching upon the great basin of the Lawrentian Lakes, destined soon 
to be one of the grandest commercial avenues upon the continent. This it does at the sources 
of the Genesee Eiver, in Potter County, and in Erie County, near the lake of that name. Thus 
it shares with New York the rare privilege, possessed by no other State of the confederacy, of 
holding the head- waters of the three great river-systems of the eastern half of the continent, a 
drainage to the Atlantic, to the Gulf of Mexico, and to the Gulf of St Lawrence. In physical 
position, therefore, as in other respects, these two noble territories, placed at the focal water-shed 
of this widely-diverging drainage, may justly be regarded in the light of a double keystone to 
the orreat dome of the Union. 

GENERAL WATER -SHED AND MAIN SLOPES. 

It will assist us to a clearer understanding of the special features of the several di^dsions of 
the State, if we first examine its primary w^ater-shed, and the chief slopes which depend from 
this. The great axis of river-drainage, of which it forms a part, after separating the Atlantic 
streams from those which flow into the lakes and into the Ohio River, and pursuing a very 
meandering course from near Lake Champlain, south-west across New York to the sources of 
the Genesee River, and the N. and W. branches of the Susquehanna, enters Pennsylvania in 
Potter County, between the head-streams of the Genesee and those of the Tioga. Here the 
ground has an elevation of from 1650 to 1700 feet. The line of water-shed, in crossing 
the State, observes a general S.W. course, winding through the counties of Potter, M'Kean, 
Elk, and Clearfield, into that of Indiana, dividing Pine Creek from the Genesee River, and then 
separating the head-streams of the Sinnemahoning, first from those of the Alleghany, and then 
from those of the Clarion, and, further south, the sources of the West Branch from those of the 
Red Bank and Mahoning. In Indiana County the line alters its direction, and runs S.E. 
through Cambria to the crest or south ridge of the Alleghany Mountain, dividing the upper 
waters of the West Branch of Susquehanna from those of Conemaugh. Turning again at the 
Alleghany Mountain, a few miles west of Hollidaysburg, the water-shed pursues the summit of 



CHIEF NATURAL DIVISIONS. 



3 



that ridge, or rather table-land, the whole distance to the south-eastern corner of Somerset County. 
There it deflects gently S. round the western springs of Wills' Creek, which it divides from the 
eastern feeders of Castleman's Eiver, and reaches the crest of the Savage Mountain about the south- 
ern boundary of the State. This summit-line between the eastern and western waters observes 
a gentle undulation in its level above the sea. First slowly rising from its mean elevation of 
1650 feet in Potter County, it reaches about 1900 feet in M'^Kean, at the sources of the Drift- 
wood branch of Sinnemahoning, and thence it very gradually declines all the way to Indiana 
County, where, near the extremity of Chestnut Eidge, it is about 1200 feet ; thence it ascends, 
first gradually and then rapidly, to the Alleghany Mountain, upon the summit of which, between 
the waters of the Juniata and the Conemaugh, it has an elevation of 2790 feet. From this 
its maximum level, the crest of the mountain, with which it coincides, very gently declines 
to an elevation of about 2550 feet at the sources of Wills' Creek, and with nearly this elevation 
the water-shed passes southward into Maryland. 

From the above traced backbone of the land — if an axis of drainage so little prominent 
above the rest of the surface can be so styled — t^ie general level declines both ways ; E. 
towards the Atlantic, and W. towards the immediate valley of the Alleghany or Ohio Eiver. 
The south-eastern slope, which is by far the longest, though a nearly continuous inclined 
plane, when we regard the floor upon which the drainage descends towards the sea, has a 
curved or almost arched form when we view it in profile, and trace it through the summits of 
the table-lands and ridges of the Appalachian Chain. In other words, the main crest of the 
Alleghany Mountain, though it springs from a lower base than the primary water-shed, is higher 
than the sources of the streams. 

The district west of the primary water-shed is not a simple slope even at the level of its 
streams, but is a great irregular trough, the terminal portion of the basin of the Ohio Eiver, 
undulated in its south-eastern corner by the ridges called Negro Mountain, Laurel Hill, and Chest- 
nut Eidge, and bounded N.W. by a flat water-shed dividing it from a series of short streams that 
descend to Lake Erie. The north-western boundary of the western basin, or the water-shed 
separating the streams of French Creek and Chenango from those of the Ashtabula, Conneaut, Elk 
Creek, and other tributaries of Lake Erie, has a mean height in Erie County of about 1200 feet. 

Thus, dividing the State hydrographically, we find it to include three natural areas— 1st, 
A great eastern slope, descending from the primary water-shed to the tide-water plain of the 
Atlantic sea-board ; 2d, A great irregular trough, descending S.W. from the northern boundary 
of the State on the confines of Potter, M'^Kean, and Warren counties, and watered by the 
feeders of the Ohio Eiver ; and, 3d, A narrow slope in Erie County, declining to the lake. 

Orographically regarded, or classified in accordance with its external features, or the contour 
of its upland surface, and not by the planes of its drainage, the State admits of a somewhat 
difierent subdivision. So viewed, it embraces five naturally distinct regions. 

The First is that of the Atlantic Slope, a district in the S.E. angle of the State, embraced 
between the tidal waters of the Delaware and Susquehanna, and the S.E. base of the first main 
range of hills, the South Mountains. 

The Second comprises the whole Appalachian Chain, restricting the definition of this to all 
the ridges and table-lands included between the S.E. base of the South Mountains and the 
summit of the so-called Alleghany Mountain. 



4 



OROGRAPHY AND SCENERY OF FIRST DISTRICT. 



The Third comprehends all the country N. and N.AV. of the Alleghany Mountain, except 
the two districts north of the northern table-lands of the bituminous coal-fields — namely, that 
in the N.E. part of the State occupied by Susquehanna, Bradford, and a portion of Tioga 
counties, and that in the N.W. l)y Erie, Crawford, and the northern half of Warren. 

The Fourth is the just named district in the N.E., watered by tributaries of the North 
Branch of the Susquehanna. Though drained hj an Atlantic river, it belongs orographically to 
the valley of the St Lawrence, being the first or highest of the succession of plains or terraces 
by which the surface descends to Lake Ontario. 

The Fifth is the already mentioned district lying outside and N.W. of the plateau fringing the 
bituminous coal-field in Warren and Crawford counties. In the slope of its surface, though not 
in all its drainage, it belongs to the basin of Lake Erie. 

OROGRAPHY AND SCENERY OF THE FIRST DISTRICT. 

The first district, or the portion of the Atlantic Slope embraced within the State, is a beauti- 
fully diversified, undulating, fertile plain, rising from a few feet above the level of the sea to the 
base of the South Mountain, where, at the Delaware Eiver, it has an elevation of about 150 feet^ 
at the Schuylkill of about 175, and at the Susquehanna of about 300 feet. While it thus 
gradually rises northward, it observes a still more gentle ascent south-westward, or in the longi- 
tudinal direction of the great zone, of which it forms a part, and which, starting from the tide- 
level of the Hudson, slowly ascends to a height of more than 1000 feet at the sources of the 
Eoanoke in North Carolina. That the Pennsylvanian portion of the Belt steadily increases 
in altitude the whole way from the Delaware to Maryland, is plainly visible, so soon as we 
compare together the elevations above cited, at which its upper margin is intersected by its 
great rivers, the Delaware, Schuylkill, and Susquehanna. 

A more than usually diversified geological constitution confers upon this tract much variety 
of pleasing scenery. Above the level of its comparatively smooth general surface rise numerous 
hills and low ridges of swelling outline, and within the plain are some exceedingly lovely and 
richly cultivated valleys. A prevailing softness of contour distinguishes its lower portion 
especially. This is attributable to a general absence of the harder igneous rocks and coarse 
sandstones, and to the presence of the easily rotted and crumbled varieties of gneiss, semi- 
metamorphic schists and limestones which underlie the surface. The northern half of the plain, 
composed for the most part of a broad zone of friable red shale and argillaceous sandstone, 
exhibits even smoother lines of landscape, except where dykes and ridges of a greenstone trap- 
rock, protruding themselves through the softer mass, constitute almost the only rough ground 
and abrupt slopes to be found in the whole district. The entire plain was originally heavily 
wooded ; and many of its eminences, especially the more stony hills and steeper river-banks, 
still remain so, though in very few instances with any remnants of the primeval forest. 
Its larger rivers flow for the most part between high banks ; those of the lower Susquehanna are 
by far the boldest, ascending abruptly from 100 to even 200 feet above the water. 

This favoured district of the State, blessed with a temperate and salubrious climate, with a 
fertile soil, and a large share of mineral wealth beneath it, is at the same time admirably irri- 
gated. It is traversed by the lower sections of the three noble rivers, the Delaware, the Schuyl- 



OROGEAPHY AND SCENERY OF SECOND DISTRICT. 



5 



kill, and the Susquehanna, and by many beautiful lesser streams their tributaries, some of which 
are themselves true rivers in the capaciousness of their drainage. Abundantly and steadily 
watered by light rains and frequent showers throughout all periods of the year, saving occasionally 
a few weeks of drought in summer, and with a total annual rain-fall of nearly 40 inches, few 
parts of it, however limited, are destitute of fertilising running brooks. Altogether it, and the 
corresponding tracts in New Jersey and Maryland, maybe esteemed the garden of the Atlantic 
Slope. 

Scenery. — A fair conception of the river-scenery of this district may be derived from the 
pictorial section of the Schuylkill between Philadelphia and Norristown, that of the Susquehanna 
at Columbia, and that between AVrightsville and Havre-de-Grace, as likewise from the sketch of 
the Wissahickon near its mouth. One of the most picturesque ranges of river-cliffs within this 
region is the bold escarpment of red sandstone in Bucks County on the Delaware, called the 
Nockamixon Rocks. The larger rivers have a scenery peculiarly their own ; they are broad and 
very shallow, and, except when swollen Avith freshets, disclose the outcropping edges of the 
harder strata across which they flow, and which cause long reaches of rapids that impart a lively 
effect to the landscape. All of these streams, the Susquehanna more particularly, are studded 
with small islands and low bunches of rocks, richly clothed with trees and shrubs, drooping their 
branches into the swiftly-passing current. These constitute one of the most attractive and 
characteristic features of the river-scenery of the district. The accompanying sketch of a scene 
on the Schuylkill, including the upper part of the manufacturing town of Manayunk, will convey 
some notion of the aspect of the smaller shallow river-channels, where the outcrops of the strata 
are naked. 

OEOGEAPHY AND SCENERY OF THE SECOND DISTRICT. 

The second district, or that part of the Apjjalachian Chain which traverses the State, is a 
mountain-zone of very uniform general aspect, though internally and locally of much diversity 
of structure and scenery. It is remarkable for the extraordinary length, slenderness, steepness, 
evenness of summit and parallelism of its multitudinous crests or ridges. It is constituted of 
five well-marked parallel belts, stretching from N.E. to S.W., which, viewed in geographical 
order north-west wardly, are — 1st, the South Mountains, Highlands, or Blue Ridge ; 2d, the 
Appalachian Valley ; 3d, the Central Appalachian Ridges ; 4th, the Sub- Alleghany VaUey ; 5th, 
the Alleghany Mountain, or S.E. escarpment of the Alleghany Plateau. 

The South Mountains, or First Belt, is the name given to two entirely detached ranges of hiUs, 
the one extending from the Delaware River, below the mouth of the Lehigh, to the Schuylkill 
River at Reading ; the other, from Maryland to a terminating point on the confines of Cumber- 
land and York counties, 10 miles S.W. of the Susquehanna. The first of these ranges, a 
prolongation of the Highlands of New Jersey and New York, and of the Green Mountains of 
Vermont, is a belt of compactly set, short, Avood-covered ridges and hills, the whole from 5 to 
10 miles broad, embracing some pleasing agricultural valleys. Their average elevation 
above the plain S. and N. of them scarcely exceeds 600 feet ; but being abrupt and stony, 
and presenting a marked barrier to the view, they receive the name of mountains, fitly enough 
applicable to other parts of the chain, of which they are but the termination. The other 



l' 

6 



OEOGKAPHY AND SCENERY OF SECOND DISTRICT. 



range is in like manner tlie north-eastern termination of the Blue Eidge of the Southern States, 
a comparatively lofty and broad mountain-belt of singular continuity and great persistency of 
feature. It also has a very moderate elevation within the State of Pennsylvania, none of the sum- 
mits rising to a higher level than 600 or 700 feet. There is nothing remarkable in the topo- 
graphical structure or scenery of either of these divisions of the first belt of the Appalachian 
Zone. It is only where the Blue Eidge is notched to its base, at the Potomac Eiver, 
that Ave meet witkan approach to grandeur and pictorial beauty. There the mountains springing 
abruptly from a low base, and exposing some grand ribs and ledges of fissured and shattered 
rock, and the swift river obstructed by jagged reefs and islands, fonn together a scene which 
contrasts strikingly with the prevailing tameness of other parts of the same range in Mar)dan,d 
and Pennsylvania. 

The Appalachian Valley, or Second Belt of the chain, bounded south by the South Moun- 
tains, and north by the Kittatinny Eange, and styled in Pennsylvania the Cumberland or Kitta- 
tinny Valley, has the character of a long, nearly straight, and moderately undulating plain. Its 
breadth varies from about 10 to 18 miles, and it stretches entirely across the State from the 
Delaware Eiver to the Maryland line. In this distance the valley rises from an average leA^el of 
200 feet on the borders of New Jersey, to one of more than 600 feet, where it passes into 
Maryland. Its height is about 250 feet at the Schuylkill, and nearly 350 feet bordering the 
Susquehanna. At Carlisle the level is 500 feet, and at Chambersburg 600 feet. The lowest 
level within the valley in Pennsylvania is at Easton, at the mouth of the Lehigh, where the 
height above the sea is no more than 165 feet. Its gradual ascent S.W. conforms to the 
general rise of the entire Appalachian Valley, from the Hudson, where it is washed by the tide, to 
the interior of the State of Virginia, where its height considerably exceeds 2000 feet ; and it 
is in accordance, indeed, with the general gradual lifting of the entire mountain-chain in the 
same direction. The longitudinal outline of the valley is somewhat undulating, due to gentle 
bendings and to abrupt offsets in the mountain-ridges Avhich confine it. From the same causes 
it assumes several rather sudden contractions and expansions. Thus a few miles eastward of the 
Schuylkill, a change southward in the crest line of the Kittatinny Mountain shifts the north 
boundary of the valley some four miles to the south, contracting the width from 17 to 11 
miles ; but a little west of this, the plain suddenly widens by the falling ofi" of the South 
Mountain in a series of fingers, until at the Schuylkill its breadth amounts to nearly 18 
miles. West of the Schuylkill it contracts again to less than 13 miles at Womelsdorf by 
the intrusion of an outlier of the South Mountain called " Millbaugh Hill." Near Lebanon 
it is some 15 miles broad. It again soon contracts to 10 or 11 miles, and retains with 
slight variation this average breadth to Franklin County, the chief irregularity in size and 
direction occurring in Cumberland County, where the Kittatinny Mountain falls back by two 
ofisets to the N.W., deflecting at the same time more southward. From Chambersburg to 
Maryland the plain grows rapidly broader by the successive subsidence of finger-like spurs of the 
South Mountain or Blue Eidge, and by the termination of the Kittatinny Mountain at Parnell's 
Knob. At the southern line of the State its width measures nearly 20 miles. Though in 
certain tracts the surface of this fertile and beautiful plain, especially near the northern boundary 
of Lehigh, Berks, and Lebanon counties, is someAvhat broken and hilly, it is noAA'here interrupted 
as it is in Virginia, Tennessee, and New York, by rugged and lofty ridges. Only a very small 



APPALACHIAN RIDGES. 



7 



portion, indeed, is too rough and stony for the plough, and being by nature admirably watered 
with abundant rains, feeding innumerable streams and brooks, it is one of the most productive 
districts of the State. It is as fortunate, too, in its adaptation for manufacturing industry as for 
agriculture ; for besides possessing through its streams, some of which are rivers in their magnitude, 
an enormous water-power, it has vast treasures of the finest Hematitic iron ore ; has more than 
half its soil underlaid by limestone, and through half its length is in close proximity to unfailing 
supplies of fuel from the Anthracite Mines of the First Coal-basin. Seated between the Coal- 
Fields on the one hand, and the Tide-Water Markets on the other, and enjoying a climate and 
soil favourable to the highest agricultural productiveness, this valley and the Atlantic Slope below 
it, have, within the last twenty years, since the development of the mines, experienced a progress 
in wealth surpassed by few other portions of the land. 

The Scenery of the Kjlttatinny Valley, though not impressive or specially picturesque, is 
generally pleasing, and in some localities, where favourable views are procured of the receding spurs 
of the South Mountains, or of the terminal knobs and river-passes of the Kittatinny Mountain, 
it is bold and fine. More usually, however, the general evenness of the plain, and the extraordinary 
levelness, straightness, and regularity of summit of the Kittatinny or Blue Mountain, impart a 
tameness and monotony to the landscape. 

One of the best general views of the Kittatinny Valley in its breadth, with the Kittatinny 
Mountain in the background, is procurable from an outstanding spur of the South Mountains in 
New Jersey, called " Jeww?/ Jwmp," nearly opposite the Delaware Water-gap, and distant from 
it about 12 miles. The broad plain of the valley fills all the middle distance of the landscape, 
while the straight and singularly level crest of the mountain is spread before the observer 
throughout an enormous length. To the left of the Water-gap he sees a half notch in the smooth 
crest called the " Wind-gap" and further west, the river pass or water-gap of the Lehigh, distant 
more than 30 miles. The rolling surface of the valley is pleasingly diversified by farms and 
patches of woodland ; and on the right of the picture, in full view from the observer's station, is 
the picturesque little village of Hope, formerly a Moravian settlement. 

Another, and even more attractive, view of the valley is obtained from any open position on 
the point or summit of the Neversink Mountain, south of Reading. Here the valley is very 
broad, and the Kittatinny Ridge far in the distance. Seen from a high point, and through a 
clear atmosphere, it is hke a straight blue wall, notched at the pass of the Schuylkill. Tt is 
called the ''Blue Mountain" evidently from the circumstance that the earliest generation of 
settlers seldom beheld it nearer than at this blue distance ; the whole plain between being for 
a period an almost pathless forest. At the present day the valley is a well cleared, highly 
cultivated district. Its northern side is somewhat hilly and broken, embracing a chain of rather 
barren ridges of slate, but its middle and southern belts are smooth, fertile, and well tilled. The 
special landscape here referred to includes several beautiful reaches and bendings of the gently- 
flowing Schuylkill, spanned by bridges, and traversed by a broad low waterfall, caused by a dam 
diverting the water into a canal which skhts the edge of the river. It is a picture full of 
attractive objects, beautiful long slopes, and waving lines imparting a certain breadth which 
characterises all the softer parts of this great valley. 

The Third or broad central Belt of the chain, or that of the Appalachian ridges proper, 
may be described as a complex chain of long, narrow, very level mountain-ridges, separated 



8 



OROGRAPHY AND SCENERY OF SECOND DISTRICT. 



by long narrow parallel valleys. These ridges sometimes end abruptly in swelling knobs ; 
sometimes taper off into tlie valleys, in long slender points. Their slopes are singularly 
uniform, being in many cases unvaried by ravine or gully for many miles ; in other instances 
trenched at equal intervals with great regularity. Their crests are for the most part sharp, 
and they preserve an extraordinary levelness, only here and there interrupted by indentations 
or notches, some of which descend to the valley levels, and give passage to the streams and 
rivers of the country. The whole chain being the combined result of an elevation of the 
strata or earth's crust in long, slender, parallel waves, and of excessive erosion of these 
waves by water, the ridges, which are but the remnants of the wasted strata, are variously 
arranged in groups with long and narrow crests, some of which preserve a remarkable straightness 
for great distances, while others bend with a prolonged and regular sweep. In many instances 
two narrow, contiguous, parallel mountain-crests unite at their extremities, and enclose a deep, 
narrow, oval valley, which with its sharp mountain - sides bears not unfrequently a marked 
resemblance to a long, sharply-pointed, slender canoe or skiff. There are two classes of these 
boat-shaped valleys ; one possessing a synclinal structure, or with the higher strata in t"Le middle 
of the trough, and the lower harder rocks forming the steep, narrow, enclosing mountains ; the other 
having the anticlinal form, being valleys scooped longitudinally out of the summits of the great 
original crust-waves, by an excessively energetic erosive force of waters cutting through the 
harder upper strata into softer lower ones. Both classes, though thus begirt by steep, sharp, and 
very strong ridges, are usually easily entered by more than one notch or gap, affording passways 
to the streams. These gorges constitute a most important feature in the hydrography of this 
mountain-belt, as they permit a ready transit at the general water-level of the country, through 
and among crowded and steep mountain-ridges, which, wherever they are absent, are found to 
be difficult of passage, even for common roads. It is through them that aU the main Atlantic 
rivers of Pennsylvania wind their unobstructed way to their tidal estuaries, for it is a feature in 
the drainage of this whole slope of the State, that its chief streams have their sources, either 
behind the mountains or near their further border, descending across the entire breadth of the 
chaiu) Interspersed among the narrower ridges and valleys are here and there wide tracts of 
mountain table-land of the general height of the narrow-crested ridges : some of these are formed 
by the merging together of two or more ridges, which usually flatten out before they coalesce ; 
others are broad synclinal plateaus, or high, flat, mountain-basins, subdivided at their ends into 
a series of spurs, projecting forwards as the human fingers do from the hand ; a structure which 
has resulted from the presence of undulations in the strata, and the erosion or removal of their 
exposed or anticlinal portions. 

distances. — As an interesting example of the class of long, narrow, very level ridges, we may 
cite the Kittatinny Mountain or first range north of the Appalachian Valley. Commencing near 
the Hudson, close to the village of Eoudout, it stretches away to the S."\V., crossing part of 
New York, New Jersey, and all Pennsylvania to Franklin County on the border of Maryland, 
a length approximately of 240 miles. Throughout this course it is a continuous mountain- 
ridge, which nowhere subsides, but only here and there shifts its crest-line, by a jog or ofl'set, 
and has no interruption but at the five river-passes, or water-gaps, by which the rivers Delaware, 
Lehigh, Schuylkill, Swatara, and Susquehanna flow through it. It is therefore well entitled 
to its name, which, in the language of the Delaware Indians, means the Endless Mountain. 



ANTICLINAL VALLEYS. 



9 



Many other instances of very long, slender, regular ridges might be adduced, as the Mahoning or 
Second Mountain, north of tlie Kittatinny ; the Tuscarora Mountain in Juniata County ; Jack's 
Mountain, in Mifflin ; Bald Eagle Mountain, running from Lycoming, through Clinton and 
Centre into Blair and Tussey Mountain, in Blair and Bedford ; but nearly all of these are 
members of groups of ridges, to be described in detail hereafter. 

Annexed is a Sketch showing the Kittatinny Mountain in the distance, and the Mahoning or 
Second Mountain in the middle space. The foreground is the stony crest of the Sharp Mountain, 
near the Lehigli Summit Mines. This picture will convey a good conception of the features of 
our monoclinal ridges, with their level crest-lines, their occasional notches, and steep forest- 
covered slopes. 

The instances of long and narrow valleys of anticlinal structure, or where the strata dip 
away from the central line of the excavated trough, and not towards it, are, as in the cases of a 
synclinal structure, very numerous. An interesting example is that of Path Valley, in the north- 
western corner of Franklin County. Another more symmetrical one is Kishicoquillas Valley, in 
Mifflin. Both these are of simple anticlinal structure at their western ends, but contain several 
waves of the strata at their eastern, causing them to subdivide into long slender prongs. 
Kishicoquillas Valley has three such very regular prongs, like a fork, separated by high single- 
crested synclinal ridges. Penn's Valley is another instance of the same structure, forking 
eastward. The largest of all is Nittany Valley, enclosed eastward by the table-land which 
joins Bald Eagle Mountain to Nittauy Mountain, and westward by the coalescing of Bald Eagle 
Mountain with Brush Mountain. Only the lesser anticlinal valleys, such as Nippenose Valley, 
Sugar Valley, and Black Log Valley, which contain no more than one regular anticlinal llexure, 
are of strictly symmetrical form. Some of these are extremely slender, being excavations in the 
l)acks or crests of long narrow and steep waves of the strata; others, such as Nippenose and Mos- 
quito valleys, are more oval in form, the denuded crust-waves out of which they are scooped 
being broad and flat. 

These anticlinal valleys, even the most slender and regularly terminated, bear much less 
resemblance to a narrow tapering canoe than do the synclinal troughs, unless we liken them to 
a narrow boat turned bottom upwards, with the bottom or keel carved out. Instead of their 
mountain rims or crests ascending towards their ends to unite in a peak, like the prow and 
stern of a skiff", they run level to near their junction, and the terminal single ridge sinks slowly 
tapering off", like the cutwater of a slender inverted bark. 

The mountain-sides enclosing the anticlinal valleys present quite diff'erent contours from 

those embracing the synclinal. The latter, for the most part, descend with very regular flattening 

curvature of slope, or if they are terraced, as they frequently are in the anthracite coal-basins, 

the benches are narrow, and too obscure to form a feature in the landscape, except in rare cases ; 

they are, moreover, seldom gashed by numerous and deep ravines ; whereas the slopes of the 

anticlinal valleys are usually conspicuously terraced and carved by sharp gullies commencing 

sometimes in the crests of the ridges, but more frequently in the edges of the broad shelves 

running horizontally round the valleys at different levels on the mountain-flank. Beautiful 

cases of this terraced structure are to be seen in all the middle and north-western anticlinal 

valleys of the chain west of the Susquehanna. It occurs conspicuously in Black Log, 

Kishicoquillas, Penn's and Nittany valleys, and their branches, and also in ]\Iorrison's, Friend's, 

B 



10 



OROGRAPHY AND SCENERY OF SECOND DISTRICT. 



and INIillikin's coves, in nearly all of which there is a broad and nearly level bench or terrace 
high on the slope of the bounding mountains, which from a distance looks singularly like a wide 
elevated beach formed by j)ent-up waters. Such, however, was not its origin, as we shall prove 
hereafter. In those valleys of anticlinal structure, or outward-dipping stratification, such as 
Nittany Valley and Morrison's Cove, where the inclination of the rocks is very steep, the terrace 
is proportionately high towards the main crest ; and where the dip is nearly or quite perpendicular, 
and the rocks are equally hard and massive with those in the chief ridge, it becomes a secondary 
summit as lofty as the primary one, and the mountain is then strictly double-crested, with a long 
shallow grove or depression between its two sharp ridges. 

Wherever these anticlinal valleys subdivide, the mountain-spurs which separate their forks 
being terraced like the more continuous enclosing ridges, and the terraces or benches being 
composed of resisting strata, lower in position than those forming the upper main-crests, the 
latter are obliterated for a greater or less distance short of the terminations of the shelves ; and 
thus high synclinal ridges are seen rising centrally out of the tops of lower, broader ones, which 
themselves ascend many hundred feet above the level of the valleys below. These mountains, 
seated upon mountains, are curious and impressive features in the orography and scenery of 
Kishicoquillas and the other forking anticlinal valleys. A clearer conception of their aspect will be 
gained by inspecting the geological map, and the picture of Kishicoquillas Valley here presented. 

A glance at the map will suffice to show how much more extensively the mountain flanks 
facing the anticlinal valleys are slopingly trenched and guttered, than those looking into the 
synclinal troughs. 

It will materially assist our conceptions of the topographical features, or external structure of 
this mountain-zone of the State, if, in this place, we devote a little attention to the several kinds of 
mountains and valleys of which it is constituted. The elongated, narrow form of the ridges, 
their general steepness, sharpness, and levelness, have been already adverted to, and mention also 
has been made of the synclinal and anticlinal valleys, and of the table-lands ; but as there are 
several kinds of ridges, plateaus, and valleys, each class having a distinctive configuration or 
orographic character dependent on its geological structure, it is expedient that we should define 
them, and show with what conditions of stratification they are connected. 

Mountain Ridges and Valleys.— T\\q ridges or elongated, narrow, continuous tracts of high 
ground, both those of mountain elevation and the lesser ones, entitled to the name of long, slender 
hiUs, are of three orders, resulting from three difierent forms of the strata composing them. In 
geological language tliey are of anticlinal, synclinal, and monoclinal structure. When it is 
considered that every part of this zone of the Appalachian Chain owes its relief to a diflused 
and powerful cutting or wearing action of waters upon a broad group, or series of groups of great 
parallel undulations of the strata, or more or less compressed waves in the earth's outer crust, it 
is apparent that there can exist but three forms of ridges and valleys : 1st, Those consisting of 
strata bent convexly upward, or dipping anticlinally ; 2d, Those consisting of strata bent 
concavely upward, or dipping synclinally ; 3d, Those consisting of strata not recurved in either 
of these modes, but dipping only in one direction, or monoclinally, and forming the flanks of the 
waves. These three tyi)es of geological structure, shared by the valleys as weU as by the ridges, 
are each of them accompanied by distinctive external forms, or special orographic characteristics, 
only modified more or less hj the relations of the strata in regard to hardness, thickness, angle, 



ANTICLINAL EIDGES. 



11 



or dip, and other conditions affecting tlie amount of resistance they presented to the excavating 
or erosive agency of the waters. 

1. Anticlinal Ridges. — In their external form, the anticlinal ridges, whether straight or 
curved, are strictly wave-shaped. Widest and loftiest at the centre, they taper away, contracting 
and sinking to either extremity, not with a straight, descending crest-line, but with a convex, 
curving one ; indeed, they are most symmetrically and softly arched in longitudinal profile. 
Their transverse profile is likewise an arch steeper or flatter ; but the incurvation, except in the^ 
very flattest ones, is seldom symmetrical, one brow and slope of the ridge curving and descending 
more abruptly than the other. In their lower slopes, and near their base, the curvature flattens 
ofi", so that the profile is bell-shaped, though distorted from the unequal steepness above spoken 
of In some instances the anticlinal ridge embraces above the level of the valleys around only 
the upper or crest portion of a wave of the strata ; in others it takes in all the convex half of an 
undulation ; and in others, again, it includes, besides this, towards either base, the commencement 
of the concave dips of the adjoining troughs in the strata outside of it. To speak more generally, 
it depends entirely upon the relative prominence of the crust-waves, or relative depths to which 
the waters have pared away the strata from the synclinal troughs, at what level the neutral plane, 
or plane cutting through the straight parts of the flanks of the waves where the convex curves 
just cease and the concave begin, will be placed in relation to the general valley-level of the 
country. Upon its position, in an anticlinal ridge, wiU much depend the style of profile of the 
mountain, especially towards its base. Of course the foot and lower slope in all cases owes a 
portion of its flatness to the accumulation of rubbish collected there ; but in the Appalachians of 
Pennsylvania this is a thin mantle, and does not sensibly alter the shapes of the hills even where 
they pass into the valleys. 

The simple anticlinal ridges display upon their flanks and summits various degrees and kinds 
of erosion from water, dependent upon the nature of the^ strata denuded. In some cases the 
crest is grooved longitudinally into a little shallow valley ; in others, this grooving extends 
deeper, reaching soft interior rocks, and then the crest is double, and we behold the first stage 
of an anticlinal valley enclosed between two monoclinal ridges. Wherever the uppermost hard 
stratum, lapping over the summit of the mountain, has not been thus longitudinally scooped, the 
crest is smooth, presenting few notches ; but wherever the scooping has formed two narrow 
monoclinal ridges at the summit, each of these is gashed by many ravines, wide at the top, and 
contracting as they descend the flank of the ridge. 

The picture given of the Lewistown Valley, and Blue and Shade Mountains in the back- 
ground, illustrates how different the amount of erosion has been on a single-crested and double- 
crested anticlinal ridge. It displays, furthermore, in the Shade Mountain, the long tapering- 
point, and gently convex descending crest-line, so distinctive of the extremities of the simple 
anticlinal ridges. Another even more perfect example of this gradual pointing down of these 
ridges is in the north-east end of the Blue Ridge, as it may be seen from any high spot just 
above the village of Mifflintown. The Bald Eagle Mountain, as seen from Fair- View Inn, also 
shows it (see Plate) ; but the obliquity of the view conceals much of the slenderness of the point 
of the mountain. 

Instances. — Many interesting examples of anticlinal ridges, single, double, and triple-crested, 
occur in the mountain-chain. Among the more prominent may be mentioned Montour's Ridge, 



12 



OROGRAPHY AND SCENERY OF SECOND DISTRICT. 



between the two branches of the Susquehanna and Tuscarora Mountain, near the Juniata, both 
single-crested ; the Blue Eidge, south of the Juniata in Mifflin, double-crested ; and the Shade 
Mountain, east of that river in the same county, triple-crested for the greater part of its length. 
IMany of the anticlinal spurs projecting from the mountains surrounding the anticlinal valleys are 
simple or unbroken in outline at their extremities, but further along them their crests divide, 
and in some cases, where two hard massive strata form the ridge, they carry not two, but four 
secondary crests. It is recommended to the reader to inspect with care that part of the geolo- 
gical and topographical map which represents the mountain-chain south-west of the Susque- 
hanna, where he will detect all the above-described and many other curious phases in the topo- 
graphy. 

Where an anticlinal wave of hard resistino; strata is so far eroded along its summit as that the 
ridge formed by it carries a groove or shallow valley along its crest (and such is the case with 
the Tuscarora Mountain and the Blue Eidge on the Juniata), the crest-line of the mountain is not 
a gradual curve or flat arch, but a nearly straight line, terminating in two gently-descending 
curves ; it is the longitudinal profile of a truncated wave. A fair conception of the side view from 
a distance of an anticlinal ridge, deeply excavated into a valley, may be got from the picture 
given of Millikin's Cove, as it appears from Dry Eidge. 

2. Synclinal Ridges. — Eidges and hills of the synclinal structure are almost equally numerous 
with those of the anticlinal form, existing, in fact, wherever energetic denuding waters, acting 
on alternately -resisting and easily-worn strata, have cut away the harder masses from the convex 
waves of the crust, and left them only in the troughs or the concave parts. There they often 
stand forth in bold relief above the anticlinal valleys, composed of softer materials, trough-shaped 
in the curvature of their strata, yet mountains in their elevation above the general level. 
Previous to the denuding action, such ridges and plateaus were the valleys of the waves into 
which their strata were undulated ; but the ridges of those waves having been all swept away, and 
the soft materials beneath them cut into valleys, these more protected remnants of the harder 
upper rocks project above the general level. 

In some instances these synclinal ridges have narrow and sharp crests ; but this is only when 
their strata dip inwards from both sides at steep angles. Mount Pisgah, near Mauch Chunk 
(for a view of which, with its inclined plane, see the picture in this work), is a good instance of 
the narrowness in the terminating crest of a synclinal ridge or basin. Wherever the synclinal 
dip is only moderately steep, and the hard rocks are in sufficient thickness, the ridge is flat-topped ; 
and if the synclinal trough is broad, and comparatively flat in the bottom of the wave, and its 
flanks steep enough to oppose the resisting edges of the strata to the waters, we have the ridge 
spread out into a plateau. In many cases synclinal plateaus, or table-lands of hard formations, 
occupying the depressions of broad flat undulations, terminate in several subordinate, s}Ticlinal 
spurs or fingers, originating precisely in the same manner as the detached synclinal ridges, 
from the denudation of the harder strata from ofl" the anticlinal portions of a belt of waves or 
flexures. 

The side aspect or longitudinal profile of a synclinal ridge or mountain is essentially unlike 
that of an anticlinal one. While the latter is gently convex, unless where its crest is truncated, 
— and even then its ends are — this species of mountain has a crest-line slightly concave, 
especially towards its extremities. The anticlinal ridge terminates in a slowly-declining, tapering 



SYNCLINAL RIDGES. 



13 



point ; the synclinal one rises near its end into a softly-swelling liump, and then falls rapidly 
away with a bold concave sweej) into the plain. 

Even where a synclinal monutain or plateau is deeply excavated along its summit, or is but 
the extremity of a trough-shaped valley, we may still discern this slight rise at the end, and 
abrupt external slope. It is well seen in the picture of the end of Canoe Mountain in Sinking- 
Valley, the feature appearing not merely in the upper crest but in the terrace below it. 

Instances. — All the districts of the mountain-chain present us with examples of synclinal 
ridges and plateaus. The anthracite basins terminate by the converging of their bounding 
monoclinal ridges in synclinal spurs ; the long and attenuated Dauphin Basin terminates in a 
very conspicuous one. West of the Susquehanna the synclinal mountains are numerous. Kishi- 
coquillas Valley contains three such spurs, and indeed the whole remarkable mountain-group 
between the Lewistown Valley and the Valley of Bald Eagle is full of them. Nittany Mountain 
is an interesting example of one, Brush Mountain is another, and so also is Canoe Mountain, with 
its conspicuous encircling terrace. 

Two pictorial views, one representing the spurs in the eastern end of Kishicoquillas Valley, 
the other showing the termination of Canoe Mountain, are introduced to give the reader a clearer 
conception of the peculiar physiognomy of some of the synclinal ridges of the Appalachian Chain 
viewed endwise. 

The picture from Warrior Ridge, of Huntingdon and the mountains adjacent, indicates the 
very different modes of ending of anticlinal and synclinal mountains. Jack's Mountain in the 
distance is seen sinking slowly towards the right hand ; while Terrace Mountain, the high knob 
in advance of it, ends abruptly, throwing up a slight hump. 

The features of erosion belonging to synclinal ridges and plateaus differ distinctly from those 
characteristic of the anticKnal mountains. In the one instance the excavation or wash has been 
across the edges of the strata, or approximately perpendicular to their dip, this being into the moun- 
tain, the watery currents from it ; in the other, or anticlinal condition, the push of the waters 
down the slope has coincided partially with the outward dip of the beds. In the first case the 
rocks have been comparatively protected from erosion, and therefore the ravines and gutters, 
though relatively numerous, are seldom of great magnitude ; in the other, they have been in the 
attitude to be most easily ploughed up at their outcrops, and hence we find such enormous 
gashes in those crests and slopes of anticlinal and monoclinal mountains, whose strata thus dip 
coincidently with the course of the eroding waters. 

The S.E. edge of the great table-land which margins the bituminous coal-field of the State, 
and is called the Alleghany Mountain, is a good example of that excessive erosion visible in 
all the higher synclinal plateaus and ridges, consisting of nearly horizontal strata. As seen 
from near Hollidaysburg (see Picture), it displays a remarkable amount of deep trenching from 
its summit to its base. The Pennsylvania Railroad has its track through one of the ravines 
here shown, with a grade of 104 feet per mile. 

3. Monoclinal Ridges. — Monoclinal ridges, or those whose strata all dip in one direction, 
are numerous in all parts of the mountain-chain. For the most part they are the sides or 
barriers confining synclinal or monoclinal valleys, and each therefore finds its counterpart in a 
second ridge on the opposite side of the valley, containing the other outcrop of its own strata 
dipping to an opposite quarter. Viewed as isolated masses, these ridges are nevertheless 



OROGRAPHY AND SCENERY OF SECOND DISTRICT. 



monoclinal, or possess a one-way dip. It is only where the two counterpart crests unite that 
the resulting spur is synclinal or anticlinal, as the case may be. In aU the mountain-chain 
tliere is but one narrow-crested monoclinal mountain or ridge of any magnitude which has not 
its counterpart, or the oppositely dipping outcrop of its strata, within the State, and that is the 
Kittatinny, the features and great length of which have been sketched already. To make the 
rule of the basin, or rather the wave -structure of strata, universal — except in districts of original 
obHquity of deposition — it can be shown that the formations of the Kittatinny Mountain, even 
to some of their subordinate individual beds, rise again to the surface in the State of New York, 
in the direction of Lake Ontario, passing beneath our whole mountain-zone, or only rising once 
to disajDpear again, as a small anticHnal wave, in Montour's Ridge. 

The transverse profile of a monoclinal ridge depends essentially upon two circumstances — the 
relations as to hardness and thickness of the several beds of rock entering into it, and the 
inclination at which these dip. The hard rocks wiU form crests, and the edges of shelves and 
terraces, and the soft ones, depressions between the crests, and also the floors of the terraces 
themselves ; a steep or perpendicular dip is accompanied by a narrowness of base and a sharp- 
ness of summit ; and by an approximation of the crests, if there be more than one, and it 
causes the terraces to be slanting and narrow ; a gentle dip, on the contrary, spreads the 
mountain both at base and crest, converts aU but the primary summit into the margins of 
terraces, and causes these shelves to be broad and approximately flat. From considerations 
already presented, it must appear that the marks of erosion upon the two opposite flanks of a 
monoclinal ridge must greatly differ. This ma)^ readily be seen by inspecting the map, and 
some of the plates of scenery. The terraces or benches on the outcrop or basset side of the ridge 
are usually well defined, wherever the dip is neither too flat nor too near the perpendicular ; 
whereas on the other, or dip side of the ridge, they are more vague and rounded. It is chiefly 
in coal-fields, where there is a great inequality in hardness between the sandstones and the coals, 
and especially in those where the strata have a moderately steep slope, that the benches are 
clearly discernible on the synclinal aspects of the hills. Wherever they are, they furnish, as in 
some of the anthracite coal-basins of Pennsylvania, an invaluable key for detecting and tracing 
the outcrops of the seams of coal. The downward carving or grooving of the opposite slopes of 
such ridges is likewise very different ; so different indeed, in certain districts, that a shrewd eye, 
practised in reading the geology by aid of the topography, will oftentimes infer the important 
condition of dip of the strata by these features of the denudation. 

Instances. — Besides the remarkable instance of the Kittatinny ]\Iountain, we may cite as 
among the well-characterised examples of large monoclinal ridges, all those long, narrow crests 
next exterior to the mountain-rims, enclosing the anthracite coal-basins, from which they stand, 
usually, not a mile distant, insulated by a deep valley of soft red shale, and bounded outside by other 
valleys of equally soft rocks. They are to the inner citadels of fuel like so many outer protecting 
ramparts. All of these monoclinal ridges are continuous with each other, constituting, in fact, 
but one line of outcrop encircling all the coal-fields. This is readily seen. We may trace the 
monoclinal crest from the Kettle Mountain east of Maucli Chunk, through the JMahoning or 
Second Mountain to Sherman's Knob or Cove Mountain, west of the Susquehanna ; thence 
through Peter's Mountain eastward, and Berry's Mountain back again westward to the Buffalo 
Mountain near the Juniata ; and thence again eastward by the Mahantango Mountain to its 



MONOCLINAL RIDGES. 



15 



junction with the Line Mountain, and back westward to the synclinal knob which it forms with 
the Mahanoy Mountain at the Susquehanna, and again eastward through the latter to the 
Catawissa Mountain, and from the synclinal knob of this still eastward by the Nescopeck 
Mountain to the anticlinal table-land, where this unites with the Wyoming Mountain ; and so by 
this latter crest entirely round the Wyoming and Lackawanna coal-field, from whence we may 
bring it across in a flat and tortuous outcrop through the table-lands at the sources of the 
Lehigh, until we enter the Nesquehoning Mountain, and then finally turn eastward and southward 
round the Kettle to the point Ave started from. 

West of the Susquehanna numerous long and narrow monoclinal ridges encompass the 
anticlinal valleys and coves of that region all the way to Maryland. These lie in groups, which 
are more or less complex, and the monoclinals of each group may be seen to thread into each 
other in a manner very similar to the above-described winding about of the outer ridges of the 
coal-basins. Those of the great north-western belt of anticlinal limestone valleys, including the 
Kishicoquillas Valley, constitute one of the most remarkable examples to be met with in the 
world, certainly the finest case in the Apj)alachian Chain of this winding into each other of the 
monoclinal ridges due to the symmetrical disposition of the anticlinal and synclinal undulations 
of the strata. Commencing with the Bald Eagle Mountain, say opposite Williamsport, we may 
thread the monoclinal mountain - crest through ten successive anticlinal spurs, and nine 
alternating synclinal knobs, by a beautifully regular zigzag progress S. to the spurs of Jack's 
Mountain, in Union and Snyder counties ; thence trace it S.W. as the crest of Jack's 
Mountain of Kishicoquillas Valley, and back again N.E. into the Seven Mountains ; and 
thence meander it through these into Tussey Mountain, and follow it as the crest of 
Tussey Mountain to Bean's Cove, at the Maryland State line, and back again N. through 
Evit's, Dunning's, Lock, Canoe, and Brush Mountains into Bald Eagle Mountain, and along 
this to the point of setting off". In this belt of anticlinal valleys it will be observed that the 
outward projecting spurs are anticlinal, and the re-entering ones .synclinal ; whereas in the 
anthracite coal-region, where the interior valleys are of synclinal structure, the salient spurs are 
synclinal, and the re-entering ones anticlinal. And all these reciprocating, topographical 
features are the simple consequences of the planing down to one general low level of mighty 
systems of crushed waves, or parallel flexures of the strata ; the waves of the one, or anticlinal 
region, have had their hard upper rocks worn through into lower softer ones ; the waves of the 
other, or synclinal coal-district, have had their soft upper rocks cut away into lower harder ones. 

Valleys. — As already intimated, the valleys of the Appalachian Chain are of all the three 
classes which belong to a region of undulated strata ; namely. Anticlinal, Synclinal, and 
Monoclinal. They are, indeed, but the superficial depressions caused by extensive grooving by 
water of the same waves of the crust which include the ridges. It is obvious that, as the 
formations consist of alternately hard and soft, or resisting and removable deposits, a mere 
difference in the general depth to which the denuding watery currents were able to plane down 
the crust-waves, into which these strata were undulated at their elevation, would determine for 
each individual convex and concave flexure whether it would become a valley or a ridge. If at 
the time of their last retreat, or at that stage when their cutting power ceased, the moving waters 
were in contact with soft mud rocks, or as yet unconsolidated limestones, they would leave a 
permanent vaUey, whether they were just deserting the back of an anticlinal or convex wave, 



OROGRAPHY AND SCENERY OF SECOND DISTRICT. 



or the bed of a synclinal or concave one ; and if, on the contrary, they were in contact with 
less removable materials, sandstones and conglomerates, they would leave a permanent ridge 
or plateau, whether the flexure were an anticlinal or a synclinal one. 

Anticlinal Valleys. — Anticlinal valleys are of two classes — 1st, Those which terminate in 
coves, or are enclosed at their ends as well as sides by mountain barriers or ridges ; 2d, Those 
which are oj)en at both extremities, and are insulated at their sides only, by ridges of synclinal or 
monoclinal structure. Nearly all the larger valleys of the mountain-zone of Pennsylvania belong 
to the first class. After what has been already stated concerning the erosion of anticlinal flexures, 
and the scenery of anticlinal valleys, no further description of them is here needed, beyond a men- 
tion of an interesting difference between them and the synclinal valleys in the contour or profile 
of their beds. While the synclinal basins are strictly trough- shaped, or have their line of greatest 
depression of surface in their middle or near the synclinal axis of their strata, these anticlinal 
valleys are for the most part raised in the centre, and have two lines of depression — one at the 
foot of each bounding ridge. They constitute the class of excavations termed by Buckland and 
other geologists. Valleys of Elevation, and when elliptical and not too much elongated, the visibly 
dome-shaped contour of their beds entitles them to this aj^pellation. Being excavations in the 
summits of convex or anticlinal waves, they may not unfitly be called Valleys of Elevation and 
Erosion, as the denuded synclinal troughs, or those in concave flexures, may be styled Valleys of 
Depi'ession and Erosion. This bulging of the more central tracts amounts, in some instances, where 
the denuding waters have encountered a resisting underlying stratum at the anticlinal axis, to a 
positive ridge. All gradations of profile, from gently arching to prominently ridged in the centre, 
are to be met with in the anticlinal limestone valleys of the mountain-chain west of the Susque- 
lianna. Being well defined by name on the geological map of the State, and by the pale-blue tint 
employed, it is not expedient in this place to do more than call the attention of the reader to their 
topographical structure. Their physical features will be fully sketched in connection with the 
geological descriptions to be given of them in future chapters of this work. The arched form of 
surface distinctive of the larger anticlinal valleys of Clinton, Centre, Mifflin, Blair, and Bedford 
counties, and the cavernous structure of the great magnesian limestone formation of which they 
chiefly consist, combine to divert a large proportion of the atmospheric water they receive, 
from their higher middle tracts towards their sunken margins. By a drainage chiefly subterranean, 
these central tracts in Nippenose, Nittany, and Penn's valleys, in Morrison's Cove, and indeed in 
several others, are seriously deprived of superficial streams, and their soil is dry and barren, while 
their Ijorders, on the contrary, are most copiously supphed with gushing springs and large brooks 
of filtered, sparkling water. So deficient in irrigation, and therefore unsuitable to agriculture, are 
the central high grounds, that they usually go under the name of " The Barrens." Their soil is 
for the most part sandy, being derived from the disintegration of the very arenaceous lower beds 
of the magnesian limestope, and no doubt this quality concurs with the underground drainage 
above adverted to, to give them their prevailing sterility. It has been proposed to seek a remedy 
for this by sinking artesian wells, and in one or two instances sufficient supplies of water have 
been thus procured to render farming profitable, where previously it was not practicable. It is 
manifest, however, from the facts here stated, that the geological conditions are adverse to the 
procuring easily of a full supply of the subterranean water by such artificial means ; the anticlinal 
or arching dip of the strata, and their cavernous nature, being most inimical to the success of 



VALLEYS. 



17 



artesian wells. Positions may be found, however, on the slopes of these barrens or central ridges, 
where the water will rise nearly to the surface by its own hydrostatic pressure ; and in some anti- 
clinal tracts there is a flatness, or actual basining of the rocks at the summit of the anticlinal 
arch, which, where it exists even locally in these valleys, may sometimes, despite the multitudes 
of fissures and caves in the limestone, render artesian borings profitable. 

The picture of IMillikin's Cove, from Dry Eidge, displays at a glance the extent to which the 
waters were able to scoop out a valley in the crest of an anticlinal wave. 

Synclinal Valleys. — Like the anticlinal valleys, the synclinal are of two classes ; those which 
are encompassed by a rim of hard strata, and those which are open at one or both extremities. 
The several anthracite basins are good examples of the class of closed synclinal valleys both 
straight and curved, and both simple and complex in structure. The basin enclosing the coal- 
field of Broad Top Mountain, in Huntingdon and Bedford, is another good instance of a sym- 
metrical yet complex valley of this class. Many lesser ones will be mentioned in the detailed 
description of the geology. A curious example is the mountain-basin of Scrub Ridge, in Fulton 
County ; this valley being a shallow depression within an insulated mountain-plateau, ruptured 
at one side by a deep ravine. 

Of the other class of synclinal valleys, or those not enclosed at either end, there are several 
striking examples within the mountain-chain. One of the largest of these is the long valley or 
narrow plain which commences at the Susquehanna, opposite the western end of the Mahauoy 
Mountain, and ranges across the Juniata, as the valley of Tuscarora Creek, to the end of Scrub 
Eidge, above referred to. This may be regarded as a prolongation of the same synclinal trough, 
which embraces the Shamokin Coal-basin. Another very similar valley of the same structure 
is traceable through even a longer distance from the Catawissa Mountain, in Columbia County, 
across the Susquehanna, at the junction of its two great branches, and thence through Snyder, 
Huntingdon, Mifiiin, and Fulton coimties, even into Maryland, between the Black Log and 
Shade group of anticlinals on its one side, and the anticlinal ridges of Montour's Eidge and Jack s 
Mountain on the other. Its central portion is called the Lewistown Valley ; and as it is there 
obstructed by several local ridges, the whole may be as properly viewed in the light of a chain of 
valleys as in that of one single continuous trough. There is nothing especial in the scenery of 
this class of valleys to call for particular description. 

There is a subordinate class of valleys allied to these — valleys which are open only at one 
end, and usually forking there into two branches, and closed at the opposite extremity by ridges, 
or the summit of some anticlinal plateau. These may appropriately be called Synclinal Coves. A 
brief inspection of the topography shown on the geological map of the State will display the 
positions of a number of such half-shut-in valleys of all dimensions. Several large ones will be 
seen opposite the western terminations of the anthracite coal-basins, and the reader will note a 
series of them in Union County, penetrating westward from the general plain of the district, be- 
tween the beautifully symmetrical anticlinal spurs, in which the mountains of Mifflin and Centre 
counties there terminate. 

The scenery of these coves is usually striking and attractive, from the exquisite regularity of 
the curves by which the bounding ridges slope down into the bed of each glen, or further out into 
the plain that forms the middle distance of the picture. 

VOL. I. c 



18 



OROGEAPHY AND SCENERY OF SECOND DISTRICT. 



There are two kinds of these open synclinal valleys, — one terminating, as in Union County, 
in a level country ; the other subdividing or forking by the introduction, near their mouth, of a 
synclinal ridge or mountain, which itself is sometimes but the terminal knob of another synclinal 
cove of similar structure. Our map displays near the Susquehanna three interesting examples of 
this arrangement of spoon within spoon, opposite the terminations of the three first coal-basins — 
those of Dauphin, Wiconisco, and Shamokin. The two branches into which each synclinal cove, 
thus divided in its middle by a mountain basin, bifurcates, are both of them monoclinal valleys, 
or valleys, all the strata of which dip in one direction — that is, towards the synclinal axis of the 
parent valley prolonged. 

Monoclinal Valleys. — The third class of valleys consists, according to our joint topographical 
and geological classification, of those in which, as above stated, all the strata dip in one direction. 
In a region so regularly undulated as the Appalachian Chain, they are almost invariably very 
long and slender, and of uniform average width ; they are, indeed, merely excavations or deep 
trenches on the sides of the anticlinal or synclinal waves, and not on their summits or in their 
troughs, as are the other two kinds. Wherever the formations are greatly contrasted in their 
capacities for resisting the scooping power of moving water, these valleys are proportionately 
deep below the parallel crests which confine them, but in the same group of formations they are 
relatively narrow or broad, according to the steepness or flatness of the dip of the rocks, while 
their height or level above the average plane of the country is the greater in proportion as this 
dip is less. The chief variety of feature to be met with in these valleys is in the carving of the 
slopes of their bounding ridges. In many instances this is very beautiful and picturesque, espe- 
cially where the valley is large and very long, and confined by mountains, whose crests possess a 
gentle curve. If, in such cases, the observer stands on some buttress or more projecting station 
midway up either slope, he may often feast liis eye upon a long superb perspective of indented 
mountain-sides. For a reason already intimated, the ravines and terraces of the two enclosing 
barrier-ridges will ofier essentially different profiles : the one set, belonging to strata dipping 
away from the vaUey, will be sharply escarped and trenched ; the other, pertaining to beds of 
rock dipping into the valley, or with the slope of their own side of it, will be more delicately and 
faintly grooved and modelled ; and thus a rich diversity of contour is frequently to be seen, 
where the topography is of the simplest kind, and the geological structure, or dipping of the 
strata, undergoes no change. 

We get a good view of a monoclinal valley, that of the Mauch Chunk Creek, between the 
Mahoning and Sharp mountains, from a buttress of the latter, called Mount Jefierson, at the head 
of the inclined plane of the Mauch Chunk Eailroad. 

Instances. — By far the longest valley of the monochnal class is that which lies immediately 
N.W. of the Kittatinny Mountain. In strictness it stretches the whole distance from the Hudson 
Eiver at the end of this mountain, which in New York is called the Shawangunk Eange, to Perry 
County, west of the Susquehanna. Throughout its N.E. half, where it is bounded N.W. by 
the Pokono Mountain, and the whole way thence to the Schuylldll, it is a somewhat broad 
belt, and contains generally at least one subordinate anticlinal flexure, so that rigidly it is not a 
monoclinal valley. Toward its western end, however, it contracts, and runs to its termination 
without any deviation in its strata from their usual s*teep north-west inclination. This valley 
contains much fine scenery of the kind characteristic of its class, additionally diversified by the 



CLASSES OF SCENERY. 



19 



presence, on the one hand, of bold spurs entering it from the Kittatinny Eidge, and, on the other, 
by great bastions of the Pokono. 

Next in magnitude is the long curving valley immediately at the S.E. base of the 
Alleghany Mountain. This begins in Lycoming County, with the rising of the Bald Eagle Moun- 
tain, which confines it on one side. There, and in Clinton County, it is watered by the broad 
and placid Susquehanna, and by several large tributary streams entering it through deep passes 
in the plateau on its north. Further forward to the S.W. it leaves its graceful curvature of line, 
and runs almost absolutely straight between the Alleghany Escarpment and the sharp crest of 
the Bald Eagle Eidge, nearly to the termination of the latter in Blair County. Throughout this 
central part of its course it possesses the monoclinal structure on a scale of grand simplicity. 
Turning more southward in Blair, the valley widens by a curious oflset in its mountain barrier 
at the ridge called the Lock Mountain, and further on it dilates again by another offset of the 
same ridge near Bedford. The rising of Wills' Creek Mountain presently reduces it, however, to 
its average dimensions, and approaching the State boundary of Maryland, it divides into two 
branches, losing its monoclinal structure by the admission of the synclinal basin of the Potomac 
Coal-field. In Lycoming and Clinton this grand deep trench in the strata embraces a few trivial 
undulations which modify its topogra|)hy, diversifying its northern and central tracts, with a few 
small picturesque ridges of limestone. Again, in Bedford County, the introduction of one or 
more short waves of the strata, near the foot of the Alleghany Mountain, causes the presence of 
more than one knob and stony-crested ridge. Besides these more marked exceptional features, 
the valley exhibits throughout its entire N.W. border, a multitude of low hills, carved 
from out the base and lower slope of the Alleghany Mountain. These are well shown in the 
picture of the front of the Alleghany and the country at its base, taken from near Hollidaysburg. 

It is not necessary to enumerate here the many long and slender monoclinal valleys which 
begird the anthracite basins, like so many moats enclosing walled cities. The geological map 
exhibits them in all their curious symmetry, and the descriptive details hereafter to be given will 
set forth their more special features. Wherever there exists a basin within a basin, or one anti- 
clinal valley within another, two such monoclinal valleys, one on each side, will be seen to 
occupy the spaces between the rims of the inner and the outer ridges. 

DIFFEEENT CLASSES OF SCENEEY IN THE MOUNTAIN-CHAIN, AND THEIE EELATIONSHIPS 
TO THE PHYSICAL GEOGEAPHY AND GEOLOGY OF THE EEGION. 

The kinds of scenery most characteristic of the larger anticlinal and synclinal valleys have 
been already alluded to, but it will be instructive to sketch succinctly the several classes of natural 
pictures to be met with in the Appalachian Chain, with somewhat more of geological method, 
avoiding a repetition of what has been already described. 

Scenery commanded by Anticlinal Mountains. — Beginning with the views distinctive of the 
anticlinal belts — mountains and valleys— we will, in the first place, conceive ourselves standing 
on the summit of a simple or unbroken, long, narrow, anticlinal ridge. Stationed anywhere near 
the central swell of its crest, and commanding an unobstructed sweep of vision, we may usually 
behold a very interesting panorama of mountains. Looking across the chain in either direction, 
the eye descends the long, beautifully-curving, flattening slope of the mountain-side from a craggy 



20 



OROGRAPHY AND SCENERY OF SECOND DISTRICT. 



foreground, over gnarled and wind-distorted trees of stunted growth, to timber growing progres- 
sively denser and richer, till low towards the foot, and in the valley, the forest spreads away in 
broad and dense liLxuriance. Beyond the adjacent valley or narrow plain rises a counter-slope of 
another mountain-ridge similarly clothed with woods, and ending in a stony crest of nearly equal 
elevation with the summit we are upon. Our position is, however, somewhat higher than the 
crest-lines of the monoclinal and synclinal ridges around us, and the eye travelling across them, 
and through the notches which here and there indent them, or beyond their points, sees ridge suc- 
ceeding ridge, and valley behind valley, grouped in a far-receding perspective, like majestic waves 
on a storm-tossed ocean. The upper slopes of the mountains being for the most part clothed with 
forest, this resemblance to some vast sea, heaved into enormous billows, is rendered all the stronger 
from tlie monotony of the colour which clothes the wide scene. It is only in the nearer distances, 
especially in the valleys beneath us, that this monotony of tone is relieved by other brighter tints, 
by clearings, cultivated fields, the rich browns of the ploughed earth, and the gayer green of the 
meadows. It is delightfully interrupted by a feeling akin to surprise when the eye catches 
sight, through some deep notch or opening, of a patch of cultivated valley, with its farms and 
dwellings smiling in the sunshine amid the dusky green of the seeming wilderness. 

Let us now suppose that the beholder, sated with these broad mountain-top views, turns to 
gaze in the direction of the trend of the crest upon which he is standing, or towards the north-east 
or the south-west. To oi:»en these longitudinal views from foreground obstructions, he will usually 
travel along the summit and station himself somewhere upon the long drooping end of the moun- 
tain, though at as high a level as possible. There he will be greeted by a scene which seldom 
fails to interest and delight him. Very different from the previous, it is a picture of long receding 
valleys instead of opposing mountains. Centrally in the nearer parts of the landscape is the 
regularly-tapering forest-clad ridge upon whicli he stands, and beyond it a wide noble panorama, 
formed by a girdle of mountains, converging to the distant vanishing-point of the picture in a 
swelling peak, or gracefully rounded summit, the highest object in view ; and all between this 
background and the hill on which he is stationed, the more or less cultivated plain or valley 
stretches before him, and dividing at the lower point of the ridge, passes to the right and left of 
him. He is looking, in fact, towards the head of a great anticlinal cove between the mountains, along 
an anticlinal valley many miles in length, which, bounded by symmetrical mountain-slopes, opens 
towards him, and divides at his feet. In some instances, as in Centre and Mifilin Counties, these 
coves are simple, and we look along but one slender valley closing up in the distance ; but this 
style of scene has many modifications, and there are numerous examples where, besides the prin- 
cipal valley stretching in front of us, we look forward past the ends of synclinal ridges, right and 
left, into other parallel plains. Of this character are the beautiful semi-panoramic pictures to be 
seen whenever we are at the trouble to ascend to some high clear spot on the N.E. point 
of Shade Mountain, in Snyder County, or to a similar position on the Tuscarora Mountain, in 
Juniata. A little study of the topographical features represented on the map, will suggest many 
other choice points of view of this description ; indeed, there is scarcely an elevated anticlinal 
ridge within the portion of the chain west of the Susquehanna which does not, from one or both 
of its extremities, command a superb view of valleys and their bounding ridges, seen in the 
direction of their length in prolonged perspective. 

The interest belonging to this class of scenes is frequently much enhanced by a singular 



ANTICLINAL MOUNTAINS. 



21 



structure in the ends of the anticlinal mountains, from whence the beholder is supposed to be 
lookino-. Through geological causes, hereafter to be explained, the point of the mountain, 
instead of tapering off simply and smoothly, sinks with a beautiful crest-line to a certain spot, 
and there ceases, plunging, as it were, into the centre of a little crescent-shaped or horse-shoe 
valley, which closes around it, and projects its two horns or prongs backwards, to coalesce with 
either base of the mountain. Where the mountain ends somewhat bluntly, as the Shade 
Mountain in Snyder, and Jack's Mountain in Huntingdon, do, this crescent-like rampart in the 
foreground of the picture, steep and often craggy on its inner slope, and smoothly declining on 
its outer, is a beautiful addition to the scene. Where the mountain terminates acutely, as 
the Tuscarora Mountain does at its S.W. extremity, or as the Black Bog and adjacent Blue 
Eidge do at both ends, the appended ridge has, in its ground-plan, almost the form of a long and 
slender dart, projecting a keen point into the valley, and its two barbs, backwards, towards the 
main ridge. 

There is another interesting class of scenes commanded by the anticlinal mountains, in which 
long anticlinal valleys or coves terminate. These points of view are the peaks or swelling knobs 
before spoken of, as occupying the middle points of the pictures, beheld by looking from the 
ends of anticlinal spurs up the anticlinal valleys. Let the reader, studious of interpreting the 
relations of the scenery of the mountain-chain to its topography, imagine himself standing at 
the head of either of the anticlinal coves which intervene between the western ends of our 
anthracite coal-basins. Let him, for example, stand at the junction of the monoclinal ridges, 
Peter's and Berry's Mountains, or at the union of Mahantango Mountain with Line Mountain. 
He will observe two very different scenes, as he gazes eastward or westward. Eastward, he 
beholds a picture very similar to those before described, as seen from the ends of the insulated 
anticlinal ridges, only much more circumscribed, for he looks into a short anticlinal cove 
forking to liis right and left into two narrow monoclinal valleys. But westward he gazes over a 
landscape of far wider scope ; he sees the two monoclinal ridges, at whose elevated point of 
junction he is standing, diverge and recede before him in gentle curvature, like the bulwarks of 
a great ship viewed from the end of the forecastle ; while subsiding in front of him there 
stretches a long, expanding valley, hilly, and covered with wood in its nearer, narrower end, but 
smooth, cultivated, and gay with farms and villages in the distance ; and he catches here and 
there the silvery surface of one or both of the main streams which flow from him along its 
margins, or perhaps that of the main Susquehanna Eiver itself. Centrally, in the background 
of the scene, appear the ends of high-swelling anticlinal mountains, on the extremity of one of 
which we have before supposed him stationed, and gazing towards the very spot from which he 
is now looking. 

If our traveller, still restricting his attention to the commanding points of view afforded 
by the high anticlinal ridges and knobs of the country, chooses, in the same district, one of the 
points of junction of the monoclinal ridges which immediately invest the anthracite coal-basins, 
shifting his station from the outer to the inner barrier of the coal-field, — if he chooses, for 
example, a spot on the high anticlinal plateau west of Tremont, or any similar geological 
locality, — he will have before him a very curious and interesting scene. At the head of a crescent- 
shaped rim of mountain, he gazes into a deep crescent- shaped valley called " the Kettle," and 
across the middle of this beautiful valley, looks upon a broad, swelling, anticlinal mountain, the 



22 



GEOGRAPHY AND SCENERY OE SECOND DISTRICT. 



very same upon whicli he had his previous station. The deep moon-shaped valley before him 
throws forward its two horns to embrace the broad mountain in front of him, each running 
indefinitely into the distance, as a straiglit and narrow monoclinal valley between two gharp- 
crested monoclinal ridges, into which the anticlinal knob soon diverges. If his perch is high 
enough, he can look along their narrow summits, and into the valleys between them, counting 
foiu" mountain-ridges and three enclosed valleys. In the middle of the wide picture he catches 
a distant view of the expanding anticlinal plain or vaUey, which nearly filled the scene at his 
previous station, and right and left of it he beholds the narrower side-vaheys prolonged from the 
crescent-shaped " Kettle " below him. 

If, instead of selecting a series of stations on the broader anticlinal waves of the surface, our 
traveller chooses his points of look-out at the head of one of the slender hmestone coves west 
of the Susquehanna, he will meet with a series of views very similar in their general features 
to some of those just described, but differing in the comparative slenderness of the valleys along 
which he will gaze. Planting himself back from the immediate head of one of these coves upon 
the next ridge, as he did in a previous instance, he sees before him, not a deep crescent-shaped 
Kettle or valley, but a very interesting crescent-shaped plateau, or mountain-floor, or upper cove, 
beyond which he looks into the lower principal one. Some of these mountain-coves in Centre 
and Union counties are indeed somewhat depressed at their ends, and therefore approach a 
little the anticlinal " Kettles " in their scenery and topography ; and in truth the industrious 
explorer of these features of the cliain may find them of every gradation, from deep " Kettles " 
to high level crescent-shaped mountain table-lands, as the conditions of stratification permit. If 
the soft stratum forming the excavation is very thick, and the- dips moderately steep, a wide 
deep valley is the consequence ; if it is thin relatively to the hard formations embracing it, and 
the anticlinal flexure is gentle, an elevated crescent-shaped plateau is invariably met with. 

Scenery from Synclinal Mountains. — The kinds of scenes visible from the summits and sides 
of the straight-backed and level synclinal and monoclinal ridges of the Appalachian Chain are, 
for the most part, so identical with those already described, as seen from the tops of the anticHnal 
ridges, that it would be superfluous to attempt to depict them. Nor is it necessary to sketch the 
features of those which are beheld from the terminal synclinal knobs or basins, looking outwards 
into the valleys and plains, further than to indicate wherein they diSer from the scenes beheld 
from the points of the anticlinal ridges. We have seen that the latter, embracing great longitu- 
dinal views of the anticlinal valleys, are bounded by the ridges which enclose and terminate 
these coves ; they of course take in the most terraced slopes of the adjacent mountains. The 
other class of scenes, or those of the synclinal belts, likewise sometimes terminate in cove-shaped 
valleys, though they more frequently look out into plains and vaUeys which are not closed in the dis- 
tance by any converging ridges. The terminal knobs of the synclinal basins being loftier than the 
drooping points of the anticlinal ridges, these first-named stations ofier altogether the widest 
and most panoramic mountain-pictures to be grasped by the eye ; and they have this further 
superiority over the other class of summits, that they control unobstructed views in all directions 
outward from the basins to which they belong, into the longitudinal plains included between the 
receding anticlinal summits in one direction, and inward in the other, to embrace the features of the 
mountain-troughs at the ends of which they are seated. The outward view, or that which we get 
upon gazing ofi"from the synclinal basin, whether it embraces a cove or an unclosed valley receding 



SYNCLINAL VALLEYS. 



23 



to the horizon, shows the antichnal mountain-slopes in their least indented and terraced aspects, 
unless where these slopes belong, as in the case of the Tuscarora, Shade, and Blue Mountains, to 
ridges grooved along their crests, when they are deeply notched and ravined. In such instances 
the perspective is very fine, as the reader may infer from inspecting the picture of the Lewistown 
Valley, and such others as show the indented flanks of the ridges of this order. Another 
characteristic feature of these scenes is the deepness of the valley in the front of the picture, 
or that in which the synclinal knob terminates. Ending more abruptly than the anticlinal 
spm-s, these synclinal mountains usually overlook steeper slopes and deeper valleys on their 
outer sides. 

Some of the most commanding points of view of this class are the terminal knobs of the 
several Anthracite Coal-basins ; but precisely as we found, in the anticlinal stations connected 
with these basins, two different classes of commanding summits — one set belonging to the exterior 
rim of mountains, the other to the interior rim, or that immediately enclosing the Coal VaUeys, — 
so here, we find among the synclinal knobs two similarly related kinds. Each description 
of summit commands, of course, two classes of scenes, one in the direction from the Coal-basins, 
the other in that towards them. 

Views from the Ends of the Eocteinor Basins. — Let us, for the sake of more clearly under- 
standing the scenery connected with the great synclinal belts or basins of the mountain-chain, 
conceive ourselves standing on any one of the five terminal knobs in which the outer mono- 
clinal ridges encircling the coal-fields unite towards the west — namely, uj)on the ends of the 
Cove Mountain, the Buffalo Mountain, the Mahanoy Mountain, the Catawissa Mountain, or 
the Shickshinny or Knob Mountain ; or suppose ourselves in a corresponding position to the 
Broad Top Coal-field on a knob of Terrace Mountain, or that of the Harbour Mountain. From 
either of these high stations we can command one view from and another towards the coal- 
field to which the mountain -barrier is related. The outward view is wide and panoramic, 
embracing, in the middle of the picture, a long synclinal plain, extended, with gradually- 
narrowing borders, almost indefinitely before us, or finally closing by the approximation of 
the anticlinal ridges which confine it. To the right and left of the picture lies a broad 
valley, formed by the forking of this broad synclinal plain, at the base of the knob upon which 
we stand. All the mountain features, enclosing the main valley and these its two branches, have 
the soft curving lines, and graceful smooth slopes, distinctive of anticlinal ridges or convex 
undulations of the strata. 

The inward or other view is wholly difi'erent : usually far less comprehensive, it is much more 
curious and striking. In nearly each of the localities mentioned, the station is sufficiently 
elevated to enable us to embrace, at one glance, the entire structure of the mountain trough, 
upon the extremity of which we are perched. From our very standing-place, the high mountain- 
knob slopes down in a majestically flowing curve, first softly convex, and then concave ; and on 
either side it expands, throwing out two wings, which, descending and contracting in breadth, 
sweep, bending away, till they become two sharp, craggy, monoclinal crests. As the bed of the 
valley descends, these enclosing ridges sink also, but more slowly, and grow narrower, straigliter, 
and more parallel ; and now we behold a structure which may be aptly likened to the bow of a 
stupendous boat, or to a huge cradle built for holding and launching some colossal ship ; the 
difference in the dimensions being, that here miles answer to fathoms. This ability to scan with 



24> 



OROGRAPHY AND SCENERY OF SECOND DISTRICT. 



one look the vast natural trough ; to gaze downward along the high mountain-walls which 
enclose it, to behold all the planking of the ship's great hull ; the graceful divergence of her bul- 
warks, the beautiful convergence of her sides towards the central line or keel, and her far-stretch- 
ing length, never fails to fill the beholder with a sense of elation and surprise. But the scene here 
sketched carries this curious resemblance no further than to the middle distances ; for within 
a few miles, and in some instances at a less space, there rises in the centre of our fancied boat a 
mountain-knob, the sjmclinal termination of the enclosed coal-basin, and from this spot forward 
the outer trough is parted into two contracted monoclinal valleys, the same which have been 
already described as branches of the beautiful crescent-shaped anticlinal valleys designated 
" Kettles." The inner basins, or those immediately embracing the coal strata, containing no such 
central features, but being trough-like throughout, present, when seen from their terminal syncli- 
nal knobs, this resemblance to a ship or boat far more exactly. To the description of these we 
shall come presently. 

Vieics from (he Ends of the Interior Troughs or Coal-Basins. — Shifting our position along 
any of the synclinal belts, including the narrow coal-basins from the termination of the outer 
mountain-barrier to the end of the inner one, or that belonging to the immediate rim of the coal- 
field, we enjoy, as in the j)revious case, a view of two remarkable but very difierent scenes. One 
of these we behold when we look from the coal-field into the synclinal cove which encompasses the 
mountain summit upon which we stand ; the other opens itself on gazing in the opposite direc- 
tion into the coal-basin itself, which stretches away, descending and expanding, almost from the 
spot we occupy. 

The first or external picture is that of a symmetrical cove, bounded and closed by two con- 
verging mountain-crests. Stationed in the centre of the trough, we look along the valley and see 
its bed gradually contracting and rising as it recedes from us, until it lifts itseK like the, stem of 
a sharp canoe into the high peak which bounds our view in the distance. The scene is very 
analogous to that already described, as visible from an anticlinal ridge, when we look lengthwise 
into an anticlinal cove, with this difference, that we are standing on a loftier point, and behold a 
much more boat-like contour in the bed and slopes of the valley before us. The whole carving 
or modelling of the valley is difierent ; it has the softness and delicacy of curve characteristic of 
the synclinal structure, due to an accordance between the slope of the strata and the slope of the 
waters which cut them ; whereas the valleys and coves of anticlinal structure are more boldly 
seamed and distinctly terraced, through the reverse relation of the dip of the strata to the course 
of the scooping waters. 

One of the finest of this class of views is that from the end of the Dauphin Coal-Basin; 
another is that of the Valley of Zerbe's Run from the end of the Shamokiu Basin, and a third is 
from the top of Mount Pisgah into the Lehigh Kettle. 

The other or interior scene, that of the inner valley or coal-basin, is, in its simple grandeur, 
perhaps the most impressive of all. Standing on any of the mountain-summits in which, by 
the closing together of their narrow barriers, either the Schuylkill, the Shamokin, or the 
Wyoming coal-field terminates, and looking into those valleys, the beholder sees a structure 
singularly like the deck and bulwarks of a gigantic ship scanned lengthwise from the bow- 
sprit ; his point of view is relatively as high above the crests of the ridges which diverge 
right and left from him, and then trend away nearly parallel for miles towards the waist 



MOUNTAIN CRESTS. 



25 



of the symmetrical skiff - built valley, as wlieu upon the stem of an actual vessel he plants 
himself on the butt of the bowsprit, and overlooks the taffrail, the forecastle, and the deck. Of 
this class of scenes none are finer than that from Mount Pisgah, near Mauch Chunk, into the 
Lehio'h Basin : that from the end of Bear Mountain into the Wiconisco Basin : that from the 
knob of the Mahanoy Mountain, looking into the Shamokin Basin, and that from the Shicksliinny 
Mountain, gazing into the Wyoming Coal-field. In some cases a shoulder or platform on the inner 
side of one of the bounding ridges of the trough-shaped valley projects sufficiently forward into 
the valley, and is high enough, to afford a fine general picture of its interior. Such a view of the 
eastern half of the Pottsville Coal-basin, or first Great Coal Valley, is procurable from the Lehigh 
Summit Mines looking westward. It is especially instructive in displaying the slenderness of tlie 
mountain barriers of the valley and the narrowness of their crests. The Locust Mountain and 
the Sharp Mountain are well seen in profile at the notches or gaps through which the Little 
Schuylkill enters and passes out of the basin. (See the Plate.) 



SCENERY AND STEUCTUEE OF THE MOUNTAIN CEESTS. 

Having in the foregoing paragraphs sketched the general features of the several kinds of 
scenery visible from the anticlinal and synclinal summits, it will be instructive, before leaving these 
and descending into the valleys and the passes through the ridges, to look at the crests of the 
ridges themselves. 

1. Anticlinal Crests. — The mountains of anticlinal formation, when not truncated, have their 
crests usually very smoothly and regularly rounded. They are wider for the most part than those 
of the monocHnal ridges, but narrower than those of the synclinal, and they are commonly less 
flat than either ; indeed, every portion of the top may be said to have some curvature. Their 
local topography is therefore not interesting, though the distant views they command are 
unobstructed by any inequalities in the foreground. But when truncated or trenched along their 
crests, their local scenery is oftentimes pleasing and curious. If the tourist wishes to explore such 
a mountain, with a view to a knowledge of its topography and its geological contents, he will set 
out at one extremity, ascend the crest-line along the anticlinal axis to the high point where the 
crest divides, and the long oval valley or spoon-shaped mountain-basin begins, and there pause 
and scan the exquisitely beautiful curvature of the lines of the surface of the shallow mountain- 
vale. If the anticlinal structure is symmetrical, in other words, the two slopes of the anticlinal curve 
of the strata nearly equal, he will perceive a remarkable evenness and equality in the soft slopes of 
its two borders. If the ridge is denuded of its timber, he may, from his high station, see along its 
entire length, and grasp the beautiful oval curve of the narrow crest or ledge which encircles it. 
In some instances it will have the regularity of a most accurately carved, shallow sldfi" ; in others, 
one or both of its sides will be notched, and opposite to each opening will occur a depression 
in its bed. Not unfrequently the converging slopes of this trough in the top of the mountain will 
descend towards each other by successive stages, and not continuously, and the terraces corre- 
sponding in height, and looking like the benches in a boat, will suggest the similitude to a skiff 
stiU more strongly. The explorer may follow the central line or anticlinal axis through the middle 
of the high valley, and there examine the lowest strata which the denuding waters have been 
able to cut into upon the back of the uplifted wave ; and to seek the very lowest, he will go to 

VOL, I, D 



26 



OROGRAPHY AND SCENERY OE SECOND DISTRICT. 



the depressions opposite the lateral notches. Again he may walk along either of the narrow crests 
enclosing it, and obtain superb views of the external country, and, by merely turning his head, find . 
relief from the fatigue of a vast and complicated picture, in the simplicity, quietness, and home-like 
nearness of the little mountain-valley at his side. Following the more unbroken of the two crests, 
if one of them is notched, he will pass in succession the points opposite the openings in the other, 
when his eye, previously hemmed in by the rim of the valley, which is seldom more than two or 
three hundred yards distant, will catch with surprise and pleasure the far-off plains and hiUs, 
with their brightly tinted farms and houses, and frequently a shining river. Such are the con- 
trasts which refresh the geologist while toUing along the summit-ledges of the anticlinal ridges 
which so abound in the Appalachian Chain. 

2. Synclinal Crests. — The tourist finds the ascent of the synclinal ridges more abrupt and 
arduous than that of the anticlinal ones. lie meets with some, retaining a simple, narrow, 
straight crest-line for many miles. There is one such, called the "Dividing Mountain" between 
Path and Anderson's Valleys in Franklin County. The slender terminating ridge of the Dauphin 
Coal-basin is another ; and the Hole Mountain, in Lebanon, a third ; though few of them are like 
the latter, insulated from other ridges. In the great majority of instances, the single-crested liiUs of 
synclinal structure are merely long spurs, separating anticlinal valleys, and expanding into basins 
by the division of the crest into two monoclinal ones. The styles of scenery visible from both 
the terminal knobs, and from the points of bifurcation of these high synclinal spurs, have been 
already sketched. But some of the synclinal ridges have the form of long and very narrow 
mountain-troughs ; that is to say, they have been truncated, or hollowed at their crests into 
slender oval basins, bounded by two adjacent, parallel, monoclinal ledges. A good example of 
this structure is to be found in the ridge in Franklin County, terminating in Parnell's Knob. 
The local scenery of such a trenched synclinal summit is very analogous to that already depicted 
as belonging to the similarly truncated, anticlinal mountains. The slender, elevated, oval vaUey 
has the same spoon-shaped terminations, and the same notches in one or both of the barriers 
confining it. It differs chiefly in showing no platforms or benches on its slopes, and presenting 
altogether smoother and softer concave lines. 

3. Monoclinal Crests. — The mountain summits of the monochnal ridges, when longitudinally 
explored, are fuUy as interesting as those of the other classes. They indeed abound in a richer 
variety of immediately local pictures. This diversity mainly depends, however, upon geological 
conditions, that is to say, upon steepness in the dip of the strata, and especially upon a wide 
difference in the relative hardness or susceptibility to erosion of the materials of the mountain. 

Where these are nearly homogeneous, the crest is for the most part monotonous in its features, 
being simply rounded like that of an unbroken anticlinal summit ; but where they are in strong- 
contrast, the mountain-top is full of variety. To picture more clearly the appearance of these 
crests, let us suppose ourselves tracing one of those which bound the southern or middle anthra- 
cite coal-basins, where an extreme difference of hardness exists between the massive conglomerates 
and sandstones, and the thick coal-beds and clay-rocks, all composing the Lower Coal-measures. 
We will imagine ourselves proceeding westward, along either the Sharp Mountain or one of the 
ridges enclosing the Wiconisco or the Shamokin Basin. The average width of the actual top of 
the mountain is seldom more than 100 yards. It is frequently much narrower. This top is 
approximately level, but it is picturesquely broken up into a succession of long narrow floors or 



MOUNTAIN SIDES. 



27 



strips of smootli surface, each seldom more than 30 or 50 feet broad, standing at slightly different 
levels, and separated by long, narrow, jutting crags, or ribs of hard and naked sandstone or 
conglomerate, broken at their outcrops into enormous blocks. Pursuing a zigzag course across 
the summit from one smooth floor over a strong reef to another floor, we soon ascertain which is 
the highest ledge, and gazing thence, we are able to mark the exact profile or configuration of the 
mountain-top. Stretching before us and behind us, are usually three, or four, or five of these 
nearly horizontal floors or terraces, each with its supporting craggy lih of conglomerate. The 
perspective is extremely curious and picturesque. If a sparse growth of gnarled chestnut oak, 
black oak or chestnut, shades as usual the summit and sides of the mountain, we behold long 
^dstas or alleys among the trees, marked out by these alternating smootli and rocky strips. 
Shifting our position to a ledge on the outer verge of the mountain, we overlook an extremely 
steep and stony slope, and may discern one or more similar, but less level and well-defined 
benches or terraces at difierent levels below us, and beyond these a progressively smoother 
surface, growing steadily flatter, and covered with a denser forest all the way to the base. If now 
we cross the crest to the brow or shelf, looking into the basin, we behold a much less steep and 
rugged flank ; the benches are more numerous — 'each marks the outcrop of a bed of coal — but 
they are slanting, and comparatively indistinct, and the bushes and trees are thicker upon them. 
Advancing along the top of the ridge, and choosing for our path either the highest smooth floor 
or the top of the most projecting stony rib, we follow it for a distance, perhaps of some hundreds of 
yards, when it changes its relative elevation above those adjoining it, or disappears to permit some 
other bench or ledge to form the actual comb of the mountain. Thus our journey ofi"ers a con- 
stant succession of new local pictures, the path we are tracking leading us from a smooth floor, 
clothed with soft herbage, to reefs and clifi"s, and back again alternately, — sometimes to one verge 
of the mountain, to open one broad landscape to our view ; sometimes to the opposite verge, to 
substitute another, and even wider picture ; or again, along a high central crest, from whence we 
command both scenes, and can unite them into a perfect panorama. 

Aspects of the Mountain Sides. — Mention has been already incidentally made of some of the 
prevaihng features of the slopes of the Appalachian Eidges, their benched outline, faint on their 
dipward sides, conspicuous on their escarped ones, and their general vesture of forest, stunted and 
sparse towards the crests, but luxuriant and dense low down. It is now in place to speak 
concisely of one or two other features. Nearly all the higher ridges, particularly those of mono- 
clinal structure, have their flanks thickly strewn with a stony rubbish, the wreck of the disrupted 
materials of the mountain, dislodged from the outcrops of its strata, and left dispersed in wild 
confusion from its very summit to its outer base in the vaUey below. This fragmentary 
matter, which is of all sizes, from sand and comminuted shale to vast angular blocks of the bulk 
occasionally of a smaU house, is coarsest and in greatest quantity where the strata which have 
supplied it are alternately massive and soft. It would appear to prevail in greatest plenty 
near and within the deep clefts or notches of the mountains through which the floods tore 
their violent passage, and along the beds of which the comparatively puny and quiet rivers now 
find their easy channels across the chain and towards the ocean. In such localities the covering 
of loose blocks of stone above the strata and the soil is so thick, the pieces are so large, the vast 
pile so steep and pervious to the rain, that neither tree nor shrub gets foot-hold, and, as a conse- 
quence, the mountain is utterly naked of foHage. These great "stone-slides," as they are called, 



28 



OROGRAPHY AND SCENERY OF SECOND DISTRICT. 



face in some places the entii-e mouutaiu from its summit to its base, but more commonly they 
occur in enormous patches. The sandstone blocks of which they consist are usually coated with 
a dark grey lichen — their surfaces being too dry for even a green moss — and this hchen, black- 
ened by decay, imparts a singularly austere and savage aspect to the mountain-passes. We shall 
discuss in another place the question of their origin, and that of the period of their production. 

Passes, or Notches in the Mountains. — Among the local scenes characteristic of the Appala- 
chian Chain, none, perhaps, are so impressive and picturesque as the deep notches or defiles in 
the ridges. They are of two classes : indentations or clefts, which do not descend to the level 
of the adjoining valleys ; and more profound gorges, intersecting the mountains to their very 
base. The former are called " Wind-gaps," from the almost constant presence of a breeze in one 
or other direction through them ; and the latter — those at least which afford passage to the larger 
rivers — are called " Water-gaps." They are various in their forms, both as respects their profile 
and their groimd-plan. In their simplest type, these notches are mere wide clefts, the sides of 
which slope at incHnations rarely exceeding 45°, until they reach the base of the mountain, 
where, in some cases, they approxunate so closely as to leave space for only a narrow stream ; 
in others, they are still so wide apart as to let the broadest rivers flow between them. Numerous 
deviations from this regular profile are to be met with, all of which are traceable to geological 
conditions in the dip and composition of the strata intersected. I have elsewhere — in the 
pages devoted to the discussion of the efiiects of local erosion upon strata — classified the several 
forms of our mountain-gaps, and explained the origin of the many curious modifications of shape 
which they exhibit. For the present we shaU refrain from so close an analysis ; and viewing 
them only as specimens of scenery, confine our attention to such features as give them distinctive 
pictorial characters. In this fight they may be regarded as of two classes : 1st, Simple, straight, 
transverse notches, cut squarely or at a large angle across the ridges ; 2d, Complex, or wind- 
ing passes, often curving like a goose's neck. Those of the first class generally prevail where the 
intersected mountains, if monoclinal, possess but a single crest, or contain but one hard stratum, 
or where they are of anticlinal or synclinal structure. Those of the second class occur in those 
ridges which include two or more thick ribs of hard rock, separated by some easily-wasted soft 
material, and which, therefore, possess compound or double crests. The gaps in the Kittatinny 
]\Iountain, and those in most of the barrier ridges of the anthracite basins, are of the first descrip- 
tion ; while some of those cutting the monoclinal ridges of the great limestone valleys west of 
the Susquehanna, and also the ridges next exterior to the coal-fields, appertain to the second 
class, or possess the more picturesque ^vinding outline. 

The scenery connected with the simpler straight notches is rather tame, imless where the 
mountain is uniLsuaUy lofty, and where its two ends, exposed to view in the gorge, are covered, 
in whole or part, with the dark " stone-slides " previously described, and then it sometimes pos- 
sesses a degree of savage grandeur. There is, however, one form of the straight notch which 
is extremely impressive. It is when the mountain contains one great convex wave of some hard 
formation, which spans it from base to base, and exposes its ov\ti edges in the form of a majestic 
arch on each side of the gap in shattered mural precipices. Then, when the scene is large, the 
width and elevation of the rainbow-like cur'STiig clifi" impresses the sense with something 
approaching the sublime. Pennsylvania possesses a number of these arch-enclosed passes, but 



MOUNTAIN PASSES. 



29 



they are for the most part comparatively short and low. That in the Wills' Mountain in Mary- 
land, near Cumberland, is larger ; but the finest of all in the Appalachian Chain are to be seen in 
Virginia. We must go, however, to the Jura chain of Switzerland to behold these curious and 
impressive arch-formed mountain-notches in their highest picturesqueness and grandeur. 

Among the class of simple notches, the Delaware Water-gap, or that by which the Delaware 
Eiver passes through the Kittatinny Mountain, is one of the most interesting. The Lehigh 
Water-gap, being a simpler, straighter thorough-cut, is rather less impressive. It is, however, 
a good example of the class. (See the Plate.) One of the most interesting passes of this descrip- 
tion is that of Jack's Mountain on the Juniata. The denuding waters shaping this gorge, have 
not on^ made a nearly straight thorough-cut in the mountain, which here contains two great 
anticlinal waves of the strata, but they have trenched the • larger western wave so effectually 
in the longitudinal direction, as to have produced in it four terminal spurs descending into the 
pass — the four spurs resulting from two hard formations, divided into four outcrops by trun- 
cation at the top of the wave or arch, and a deep scooping down of the soft strata between and 
under them. 

Of the wider river-passes, that in the Second Mountain at the Susquehanna is a fair 
specimen. The s]&etch given (see the Plate) shows the breadth of the river and the ribbed char- 
acter of the mountain. 

The winding passes of the Appalachian Chain usually lead us into the mountain, perpen- 
dicularly to its face, and then, gracefully deflecting, take, us centrally along it, between its two 
high crests, a shorter or longer distance, perhaps even half a mile, and then, curving in the 
opposite direction, lead us out again into an open valley beyond. In this constantly -ben ding 
course we are presented with an ever-shifting variety of mountain-curve and perspective ; a 
brawling river runs at our feet on one side, and the mountain presses close on the other, generally 
clothed with timber, and here and there showing some bold buttress of rock or high impending 
crag. The scene is invariably interesting ; oftentimes it is extremely beautiful, so varied are 
the effects of light and shade ; but it is seldom grand, neither its magnitude nor style of features 
permitting it to be sublime. 

There is, perhaps, nowhere within the State, nor indeed within the Appalachian Chain, a 
more beautiful pass of this description than that through which the Lehigh Eiver flows just 
below the town of Mauch Chunk. The annexed sketch of it from the north is taken from a 
point half-way up the Sharp Mountain above the town. (See Plate.) Bear Gap, north-west of 
Shamokin, is another good example of this class of river-passes. Both of these are through the 
same group of rocks, the Subcarboniferous or Vespertine sandstones, and they are therefore very 
similar in general outline. The picture of the Mauch Chunk notch exhibits the nearer rib of the 
mountain shaved down by the waters into a long-pointed spur standing across the opening, and 
behind it the further or south rib or crest lapping past it. The same structure is conspicuous 
in the Bear Gap. In some of these winding notches the inner spur is the lowest, in some the 
outer, and in others again they are of nearly equal elevation ; and these, with variations in the 
length of the inner reach, are their chief modifications of form. The passage of the Susquehanna 
Eiver through the Nanticoke Mountain, west of Wilkesbarre, is a winding gap on a smaller 
scale. 



30 



OROGRAPHY AND SCENERY OF SECOND DISTRICT. 



GENERAL CHAEACTEE OF THE SCENERY IN THE YALLEYS OF THE APPALACHIAN ZONE. 

It is impossible to convey through written descriptions merely, to even the best-trained 
imaginations, any just conceptions of the scenery in detail of the plains and valleys of a region 
embracing so many featui'es, and composed of so wide a diversity of geographical elements. All 
that I shall attempt, therefore, will be two or three general sketches of the kinds of landscape 
which characterise the different principal classes of our valleys. 

Anticlinal Valleys. — A sufficiently full account has been given of the structure of the 
anticlinal valleys of the State, to suggest the general nature of their scenery. None of them 
present featm-es of much picturesqueness, except on a petty scale where their streams are bor- 
dered by limestone cliffs, or pass the end of some truncated ridge. The narrower ones offer 
little to the eye, except the steep flanks of the sandstone mountains w^hich confine them, or, it 
may be, one fine general picture as we gaze in the direction of their length. The wider ones, 
arched as they are in the middle, furnish many points of view, presenting rich backgrounds of 
receding mountains and pleasing middle distances of fertile champaign tracts, studded with 
farms and farmhouses, and here and there a forge or smelting-furnace. 

Synclinal Valleys. — The scenery of the synclinal valleys of the chain is so various as almost 
to baffle description. Within the coal-basins it is made up of softly undulating ciu-ves, defining 
the slopes of the bounding mountains, and the succession of nearly parallel rolling hills which 
fill the spaces between them. These hills are tame in form, being usually straight, level, and 
evenly rounded at their ends. The most pleasing pictures in the Potts^Tlle and other anthracite 
valleys are such as embrace views up or down the smaller transverse valleys of the lateral 
streams which intersect the basin, like those of Mill Creek, Silver Creek, or the West Branch of 
the Schuylkill. Some charming general views are procurable from the higher points within 
these basins — such, for instance, as that at the water-shed, or source of the Schuylkill east of 
Tuscarora, or that between the East and West Norwegian Creeks. In fact, wherever there is a 
high point — the saddle-shaped summit of a ridge in the centre of the basin, or a spur coming 
forward from one of the mountains enclosing it — we may hope, by ascending it, to get a view 
which wiU well repay us. Nevertheless, the first and second coal-fields contain but a small 
amount of scenery of that striking kind which is most acceptable to the landscape-painter. 

The synclinal valleys and plains west of the Susquehanna are, on the whole, much more 
picturesque. They are bordered by the anticlinal mountains and their many spurs, and have 
often therefore varied and striking backgrounds. The beds of these valleys are so interspersed 
with hills and forest-tufted ridges, scolloped out extensively by the waters, and are so weU 
sprinkled, for the most part, with clumps of wood amid the farms, as to furnish landscapes which, 
if they are not superb, are often really beautiful. 

There are two or three synclinal belts so unlike the rest in their topogTaphical features and 
scenery as to deserve a passing mention. I allude to the Muncy Hills on the south border of 
Lycoming County, and to the Frankstown Valley in Blair. These tracts are studded with short 
rounded hills, deeply carved and ravined, and when viewed from an elevation at a distance they 
look exceedingly like the wildly-tossed waves of the ocean, after the gale has shifted its direction, 
and raised what is called a " chopping sea." That portion of Frankstown VaUey which is included 



BROAD VALLEYS. 



31 



within the Cove of the Lock Mountain exhibits this tossed surface in a remarkable degree. (See 
the Sketch.) 

Monoclinal Valleys. — The long narrow valleys enclosed between the straight, parallel, sand- 
stone ridges of the chain, are seldom attractive in their scenery. Their features are very 
monotonous ; their surfaces are generally stony, or more or less covered with rubbish from the 
mountain-sides ; and they are, therefore, usually under forest, and this contributes much to theii* 
general tameness of aspect. For the present, therefore, we shall not linger among them. 

SCENERY CHARACTEEISTIC OF THE BEOAD VALLEYS OF COMPLEX STETJCTUEE. 

By far the most attractive scenery within the mountain-zone of the State is to be met with 
in the broad, cultivated valleys, watered by the great rivers or their principal tributaries. These 
embrace all the elements of picturesque beauty which the region possesses ; forest-covered moun- 
tains, rolhng hills, fertile spreading plains, and low verdant meadows — every combination of 
open, cultivated farm-land, lines and tufts of woodland, houses, villages, and streams ; and their 
canals, aqueducts, viaducts, and bridges. The valleys and plains, intersected by and bordering 
the great Susquehanna and its two noble branches, those traversed by its beautiful feeder the 
Juniata, and those again watered by the Delaware and its great branch the Lehigh, are full of 
landscapes, blending the bold and the beautiful. Let the tourist place himself a little way off 
from one of these rivers, or from one of their larger affluents, upon some knoll, or the point of 
some elevated spur, choosing a spot unobstructed by trees, and he will usually see spread before 
him a truly noble picture. If it is a view lengthwise, up or down the valley, he will behold on 
either hand, ridges and mountains, with their knobs, buttresses, and crests piled in fine, long per- 
spective behind and above each other, as far as his eye can reach ; lower down and nearer, and 
more in the middle of the scene, his eye will rest on a broad, rolling surface, full of patches of 
woodland, and farm, and pasture ; and again, looking deeper into the valley, he will see a succes- 
sion of cultivated terraces, each bounded by a steep and ravined slope richly clothed with wood, 
imtil descending, step by step, to where the stream or river winds through the lowest plain, 
washing the base of a line of bluffs, or spreading broad by the borders of low and grassy mea- 
dows, he contemplates its blue or silvery surface, fringed with luxuriant foliage, gleaming out and 
disappearing as he brings it in its continually expanding glories almost to his feet. More than one 
such scene will the skilful searcher after the picturesque and beautiful meet with in the Wyoming 
and Lackawanna Valley, particularly between Pittston and Nanticoke. A remarkably fine one is 
to be found between Catawissa and Bloomsburg, looking up the valley of the North Branch. 
There is another visible from the top of the Blue Hill opposite Northumberland, near the junction 
of the two great affluents of the Susquehanna, where, by a little change of position, one may embrace 
two other fine pictures of almost unequalled beauty. The view from that station northward or 
up the valley of the West Branch, embracing the reaches of the river, its islands, and the luxu- 
riant foliage of its banks and bordering low grounds, and all the boundless abundance of the 
broad cultivated slopes and swelling hills beyond, is, for an inland scene, one of almost match- 
less richness. To see it in its most attractive tints, one should behold it in the month of Jvme, 
while the foliage is fresh, and at an hour when the sun is drooping low towards the north-west 
horizon. There are many particularly attractive combinations of river and mountain scenery 



32 



OROGRAPHY AND SCENERY OP THIRD DISTRICT. 



higher up the valley of the West Branch of the Susquehanna. The sketch from Fair-View Inn 
offers a good example. (See the Plate.) 

Very charming pictures of boldly carved hills, verdant slopes, flat meadows, and luxuriant 
foliage, with a mountain on the one hand and a beautiful broad river on the other, are to be 
found in the Valley of the Delaware, at sundry places between Milford and the Delaware Water- 
gap. There are few finer views of this class than some we have seen from Fox Hill, overlooking 
Cherry Valley. There is much beautiful scenery of this description in the prolongation of the 
same belt further west. An uncommonly attractive instance is a view looking up the Lehigh 
from the solitary Eed Hill which stands fronting the opening of the Lehigh AVater-gap, at half a 
mile north of it. In the region of the Juniata, the ridge behind Lewistown commands two very 
noble pictures, one looking eastward towards the " Long Narrows," and showing the Shade and 
Blue Mountains (see Sketch) ; the other looking south-westward up the valley of the river. A charm- 
ing scene is from a hill behind Mifflintown. There is probably no river in aU the great length of 
the Appalachian Chain — rich as it is in streams flowing through fine mountain and valley scenery — 
that, for its length, passes such a succession of beautiful landscapes as the winding Juniata. 

OROGEAPHY AND SCENERY OF THE THIRD DISTRICT. 

Proceeding next in order to the third natural division of the State, or that including all the 
country N.W. of the escarpment of the Alleghany Mountain — saving the plain watered by 
the North Branch of the Susquehanna in the one corner of the State, and the slope between the 
Alleghany Eiver and Lake Erie in the other — we shall find, upon a careful examination, that it 
is a great and complex basin, edged with a more or less lofty and abrupt escarpment or steep 
sloping wall, and bounded S.E. by a low fosse-like valley, and on the N. by plains. It is, in 
fact, but the north-eastern extremity of a vast trough-shaped plain or table-land, which ranges 
hence to the interior of the State of Alabama, and which I have elsewhere designated as the 
Great Appalachian Coal-field, the longest and largest coal-basin on the globe. A glance at its 
topographical and geological features, as shown on the geological map, will make it apparent 
that the formations and the general level of the surface ascend gradually toward the north- 
east. This fact is the key to aU its external scenery. The basin-structure is shown in the 
north-westward declension of the formations bordering the region on the south-east, and their 
opposite dip where they rise again to view in the country bordering Lake Erie ; but the sim- 
plicity of this trough-like configuration is interrupted in two districts, — in the S.E. by three 
or four great waves of the strata, the chief of which form the swelling ridges of the Negro 
Mountain, Laurel Hill, and Chestnut Ridge ; in the N.E. by the intrusion of five long coves or 
vaUeys of anticlinal form, protruding south-westward into the table-land, and dividing it into six 
long, synclinal mountain-spurs. We may, therefore, appropriately separate the whole region 
into three subordinate areas, — first, the belt ranging through Somerset, Fayette, Westmoreland, 
Cambria, and Indiana counties, an undulated mountain-zone ; secondly, the belt ranging E. and 
W. between the North Branch and the Alleghany Eiver, and embracing all the northern table- 
lands of the State ; and thirdly, the area lying west of the former and south of the latter, and 
constituting the hydrographic valley of the Alleghany and Ohio Eivers southward of the Clarion, 
a country of lower levels and smoother surface than either of the others. 



SOUTH-EASTEEN BELT OE THE BITUMINOUS COAL RECHON. 



33 



1 . South-Eastern Belt of the Bituminous Coal Region. — Tlie general topographical character 
of this large natural division of the district is quite simple, though the scenery is far from 
monotonous. It is a broad, rolling table-land, traversed nearly from end to end by three wide, 
parallel mountain-ridges, and deeply ploughed in every portion of its surface, both ridge and 
valley, into ravines and hollows. North of the termination of the Negro Mountain, the belt em- 
braces essentially but two plains or main valleys, but south of that point the rising of the Negro 
Axis divides it into three. The inclination of the strata, and a prevailing absence of any very 
firmly cemented or hard beds among them, combine to exclude from this country those salient 
features which so characterise the Appalachian Zone to the east of it. The mountain-ridges, and 
even the lesser hills betw^een them, have broad, roundish summits, and comparatively gentle 
slopes, except indeed in more immediate proximity to the numerous streams which intersect 
them, bordering which the hill-sides are very steep. Many portions of the belt, particularly the 
tracts sloping into the larger rivers, are excessively eroded, and, as a consequence, the bottoms of 
the lateral ravines are sharp and narrow, and the hill-sides embracing them abrupt and rough in 
their lower portions. Unlike many of the Appalachian hills, which set out with a gentle rise and 
increase in steepness, these, for the most part, start boldly upward, and round gently off as we 
climb towards their summits. This description applies chiefly to the hills within the synclinal 
basins between the main mountains, and to the buttresses at their base, but nowise to the profiles 
of those mountains themselves, which display in their cross sections those beautiful double curves, 
convex above, concave on both sides below, which we may call the bell-shape. The immediate 
slopes or river-hills confining the great streams of the region, the Conemaugh and its main 
branch, Stony Creek ; also the Loyalhanna and the Youghiogheny and their feeders, spring steeply 
upward from the valleys, and being richly clothed with woods which retain somewhat the gran- 
deur of the primeval forest, give views up or down the deep and narrow valleys which are, in many 
instances, uncommonly grand for a scale of scenery which cannot strictly be called mountainous. 
At numerous points overlooking the Conemaugh and the Youghiogheny, we see these rapid 
mountain-streams far below us, w^orking their obstructed way along the beds of their deep glens 
for miles before us, their high wood-covered hills jutting and receding in beautiful perspective. 
This is, indeed, the prevailing picture wherever, from the upland, we look into the larger water- 
courses excavated within the main valleys or synclinal plateaus. But a diff'erent scenery accom- 
panies all the chief rivers of the district where they pass through the mountain-ridges. The 
map shows that all the principal streams — the Conemaugh and its feeders, the Blacklick and 
Loyalhanna, the Youghiogheny and its feeder, Castleman's Kiver — flow through the Laurel 
Hill, Chestnut Eidge, and Negro Mountain, by deep sloping clefts or notches, which cut them to 
the base. These mountains consist each of a broad anticlinal wave of rather gentle flexure, of 
the alternately hard and soft formations next beneath the coal strata. Each chief pass or water- 
gap is an oval amphitheatre, formed by two steep crescent-shaped mountain-slopes meeting below, 
in a nearly straight and narrow ravine, through the centre of wdiich the river flows, brawhiig 
over a rocky and obstructed channel. There is a certain simple grandeur in these scenes, espe- 
cially where the intersected ends of the mountain or sides of the gap are extensively sheeted with 
naked stone-slides of huge, grey, angular blocks, without verdure, which is not possessed by the 
steeper passes of the Appalachian Chain to the eastward. The finest views by far, are to be had 
when we stand on or near the summit of the mountain, and look midway into the notch ; we 

VOL, I. E 



Si 



OROGRAPHY AND SCENERY OF THIRD DISTRICT. 



may then usually combine with the wild foreground before us lateral peeps of the distant country 
through the ends of the gap, serving by their softness to enhance the ruggedness of the gorge or 
gulf in front. Some of the more rocky spots within these gaps, or borderiug the streams in the 
country exterior to them, are pleasing and striking pieces of local scener)^ Such, for example, 
are the Ohiopyle Falls of the Youghiogheny, and the scene near the Conemaugh Viaduct above 
Johnstown. 

But the views characteristic of this region which most impress and charm us, are those to 
be met with when we climb to the higher summits of the mountain-ridges, and find favoiu-able 
stations for gazing broadly into the country they overlook. The widest and richest of these 
mountain-views are those which are commanded by the eastern brow of the Alleghany Moun- 
tain, when we look off from almost any of its numerous boldly-jutting buttresses. These views 
embrace, to be sure, the Appalachian Zone proper, and not the belt of country we have last been 
describing ; but they are too characteristic of the position of the eastern edge of the great western 
plateau or basin, and of its dominant elevation, to be passed by, in this account of the physical 
aspect and scenery of the State. Mention was made in previous pages of the scenes visible from 
the highest central crests within the Appalachian ridges, when we gaze across the chain, and see 
crest rising behind crest, like stupendous billows in some mighty sea ; but from the stUl loftier 
positions afforded by the brow of the Alleghany table-land, we look over this billo'wy ocean of 
mountains to much vaster distances, and the pictures are proportionately more superb. 

Some interesting broad views are afforded by elevated positions high on either slope, or on 
the summit of the Laurel Hill, especially when our station gives us a sight westward through 
some broad notch in Chestnut Eidge, or over its summit, into the extended, cultivated, level 
country beyond. A fine wide scene of this kind may be had from Clifibrd's Tavern on Laurel 
Hill, looking over the Loyalhanna Gap, and another very striking one — an outline sketch of 
which is here presented — from the so-called Mud Turnpike looking westward. A most pleasing 
series of views may be procured by any one who ascends to the naked points on the western brow 
of Chestnut Ridge. With frequently beautiful foregrounds in the limestone and standstone rocks, 
forming the notched summit of the mountain, he gets a glorious expansive landscape wherever 
he gazes to the west or north into the broad plain or basin of the Ohio. He beholds a rolling 
surface, cut into innumerable softly-swelling hills, and intersected by scores of bright streams, 
covered with farms, farmhouses, and villages, shining brightly amid parks of wood and tufts of 
trees crowning the knolls, all stretching away to a seemingly illimitable distance tUl the plain 
meets the horizon. The ampleness of this field of view reminds him that he is standing on 
one of the westernmost outposts of the great Atlantic Chain, and that before him there rises no 
mountain-ridge of even the humble relative altitude of that beneath him in all the vast central 
plain of the continent till it nears the base of the Rocky Mountains. 

2. Northern Belt of the Bituminous Coal-field. — The large tract composing the north-eastern 
termination, or northern border, of the great Bituminous or Appalachian Coal-field, is sufficiently 
well defined along its northern boundary by the lower plains or valleys of Bradford, Tioga, and 
Potter counties, which penetrate between its spurs, and by the margin of the lake-slope in 
Warren, Crawford, and Mercer ; but it has no very clearly-marked southern limit in any 
physical features, passing vaguely into the south-eastern belt in Clearfield, and into the basin 
of the Alleghany River in Jefierson, Clarion, Butler, and Lawrence. The entire tract is a table- 



NOETHERN BELT OF BITUMINOUS COAL-FIELD. 



35 



land, -vrliicli rises gradually westward from the North Branch of the Susquehanna to the main 
water-shed in Potter and M'Kean counties, and declines again as gradually to the Alleghany 
River. Its mean elevation above the sea is about 1800 feet, though a few of its summits, 
especially near the water-shed and along the Alleghany Mountain, may be a little higher. 

The eastern half of this northern plateau sends forward towards the N.E. five long parallel 
projecting spurs, each having the structure of an elevated flat basin, bounded on both sides, and 
at its rounded extremity, by a steep slope, descending into an external valley. These five spurs 
are so many partially-insulated coal-basins, the extremities, merely, of the long parallel belts of 
the coal-measures, which, further towards the S.W., merge together and deepen into the Great 
Bituminous Coal-field of the State. They are the result of five anticlinal waves of the strata, 
entering the region from the N.E., and expiring within the coal-field. In consequence of this 
south-westward subsidence of the waves of elevation of the crust, the whole of this portion of 
the belt displays a slight declension of level towards the south, as the drainage of the district 
plainly manifests. A glance at this portion of the geological map discloses the curious fact that 
every one of these five mountain-spurs, in which the Great Coal-field terminates, is cut to its base 
by one or more cross valleys or ravines, through which the existing large tributaries of the West 
Branch of the Susquehanna, the Loyalsock, Lycoming, and Pine creeks flow southward through 
them. While the general surface of the main table-land and its spurs is comparatively level, 
these ra\nnes, by which it is intersected, are very deep, the hill-slopes, bordering Pine Creek and 
the West Branch and their feeders, being many hundred feet in height, and extremely steep. 
Advancing from S.E. to N.W. across these spurs, they grow relatively less elevated above their 
intervening valleys, the table-lands themselves remaining nearly at a constant altitude, but the 
levels of the valleys rising ; and this gradation continues to the high plain or valley separating 
the fifth spur from the sixth or last in Potter County, where the lower grounds, penetrating the 
table-land, are at a greater altitude than anywhere else — this district being, in fact, the common 
centre of drainage of four extensive rivers, the waters of the North Branch flowing eastward, 
those of the West Branch southward, those of the Alleghany westward, and those of the Genesee 
towards the north. 

The western portion of the northern table-land is but the north-eastern j)rolongation of the 
north-western margin of the Great Coal-field of the Alleghany and the Ohio rivers lifted gradually 
in level to a maximum elevation in M'^Kean County of about 2000 feet. It is highest on its 
eastern side or towards the primary water-shed of the State, the mean level of the surface there 
exceeding that of the north-western border near the Alleghany River by 300 or 400 feet. This 
whole tract, constituted of the fifth and sixth sub-basins of the coal-field, gradually subsides in 
level towards the S.AY., as is plainly indicated by the direction of the drainage of the Clarion and 
Alleghany, and their tributary streams. The strata decline in the same direction, but at a some- 
what faster rate than the surface does, and hence the south-western portions of the tract contain 
a greater thickness of coal-measures than the north-eastern ; indeed, in Potter, M^Kean, Warren, 
and the northern parts of Elk and Forest Counties, large tracts of the table-land are entirely 
naked of the coal-productive parts of the formation, being overspread by the conglomerate and 
other still lower formations known to underlie any workable coal-beds. The largest streams of 
the north-western border of this part of the plateau penetrate it from the north, as the feeders 
of the Susquehanna cut through the eastern district of the same belt. It is only in Potter and 



36 



OROGRAPHY AND SCENERY OF FOURTH DISTRICT. 



M'Kean counties that the south-flowing rivers have their water-shed within the State. Else- 
where, to the E. and W., they ascend into New York. Hence it is that the valleys of the 
Alleghany River and of the North Branch of the Susquehanna are destined to become extremely 
important avenues of communication between the Coal-fields of Pennsylvania and the populous 
plains of her neighbouring sister State. 

3. Basin of the Alleghany and Ohio Rivers. — After the general description of the aspect of 
this region as it is seen from the summit of Chestnut Eidge, little need be said in this preliminary 
physical sketch touching its structure and scenery. Broadly viewed, it is an extensive plain, or 
rather a very wide trough, falling gently in level from its two sides — the base of Chestnut Eidge 
on the S.E. and the water-shed of the lake streams on the N.W. — and dechning still more gradually 
south-westward in the direction of its general drainage. Its surface is, however, greatly eroded 
or trenched by converging valleys and ravines, which break it up into a multitude of branching 
little plateaus and isolated conical hills. The beds of the deeper water-courses are usually 
from 200 to 400 feet below the general level of the upland, and this inequality of levels, and a 
prevailing convexity in the outlines of the hills, impart much boldness and variety to the local 
scenery. The rocks of the region are all horizontally stratified, and are of a somewhat incohering 
texture, the least easily excavated being soft freestones and limestones, while many of the beds 
are friable shales and marls of still less solidity. These geological conditions have permitted 
the waters, which originally wasted the whole tract, to shape its surface into every degree of 
slope, from the steepness of nearly vertical cliffs to the softest and gentlest curves conceivable. 
The denuding waters seem to have flowed across the district in a broad and ponderous sheet, 
cutting first great confluent troughs and valleys, and then, when checked, flowing with a 
difl"used and subsiding drainage, carving and scidpturing its rudely-moulded slopes into e^'ery 
degree of softer contour, until the last and lightest lines impressed upon it are indescribably fine 
and delicate. 

As specimens of the more characteristic scenery of the region, I have introduced into this work 
a sketch of the country round Canonsburg in Washington County. The reader will derive a 
correct notion of the river-hills of the district, and of the aspects of the larger rivers, from the 
picture of Pittsburg and its environs. 

OROGRAPHY AND SCENERY OF THE FOURTH DISTRICT. 

The fourth physically-distinct district of the State, or that embracing Wayne, Susquehanna, 
Bradford, and part of Tioga counties, and watered by tributaries of the North Branch of the 
Susquehanna, is a country of such simple structure, that only a brief general description of it 
need be here presented. The surface is that of a rather roughly-undulated or hilly plain. Its 
eastern half, or that lying in Susquehanna and Bradford counties, is more broken and hilly than 
the parts west of the Susquehanna — a circumstance partly attributable to a difference in their 
geological composition ; the country east of the Susquehanna consisting largely of hard, micaceous, 
flaggy sandstones ; that west of the river, of a larger relative proportion of argillaceous sandstones 
and clay-shales. The whole surface is deeply trenched into slender valleys and ravines, some of 
the chief of which are thorough-cuts, passing from the East Branch of the Susquehanna, and from 
the Tioga Eiver southward to the North and West Branches. Two or three of these continuous 



LAKES OF PENNSYLVANIA. 



37 



valleys having very low water-slieds, constitute admirable thoroughfares for the commerce and 
intercourse of Pennsylvania with New York. The southern and western border of the tract has 
a deeply indented margin connected with the feature already adverted to, the existence, namely, 
of long, slender anticlinal valleys, carved out of its softer strata, penetrating south-westward 
between the high finger-shaped plateaus terminating the bituminous coal region. 

This district is not without its fair share of striking scenery. Some of the views within 
the valleys of its chief rivers, the Delaware and Susquehanna, are grand and picturesque, par- 
ticularly those visible from certain points on the edges of the table-lands overlooking those 
streams ; and the same may be said of the valleys of their larger tributaries. Indeed, few of 
the Appalachian rivers can boast a greater amount of attractive valley-scenery than the North 
Branch presents throughout its whole course, from the great bend near the State line through 
New York, and thence through Pennsylvania to the Wyoming Valley. It owes this eminence, in 
part, to the beautiful manner in which its terraces of northern drift or gravel have been strewn 
and shaped at the last retreat or rush of waters across the continent. 

A sketch, elsewhere introduced, of Spanish Hill, near Athens, in Tioga County, will convey 
some notion of the style of the hills, and of the remnant terraces of drift skirting their base. 

Lakes. — It is a curious fact that nearly all the lakes and natural ponds within the State, excepting 
those of a similarly constituted district between the Alleghany River and Lake Erie, are embraced 
within the country contained between the Delaware River on the one side, and the Lehigh and 
the North Branch of the Susquehanna, or, more correctly, the lower part of the West Branch, on 
the other. This circumstance in their distribution is the more remarkable, when we reflect on 
their almost total absence from every part of the Atlantic slope between the Hudson and 
Georgia, and from every portion of the Appalachian Chain, notwithstanding its numerous 
vaUeys, S. W. of the Susquehanna. This deficiency, which is painfully felt by every tourist in 
search of the picturesque, extends also to the whole of the western slope of the Ohio-Mississippi 
Basin, and is a distinctive feature of the drainage of the whole country south of 41° of latitude. 
In contrast with so wide and complete an exemption from this beautiful feature, there is an 
unusual profusion of ponds and lakes throughout the greater part of the country lying north of 
the above-named boundary. What can be the cause of so singular a difference in the conditions 
of the flowing ofi" of the waters 1 Simply the absence from the southern half of the continent 
of the great superficial stratum of gravel, sand, and clay, called by some geologists Diluvium, 
by others Drift, and by others, again, the Glacial Deposit. North-eastern and North-western 
Pennsylvania are just within the southern l^order of this great drift-formation, which extends 
indefinitely northward, even to the shores of Hudson and Bafiin Bays, and of the Arctic Sea. 

The broad, high table-land, in which the Appalachian Bituminous Coal-field terminates on the 
confines of New York, has evidently stopped the southward course of the nearly-spent sheets of 
water which transported the drift, and turned them south-eastward and south-westward over the 
two northern corners of Pennsylvania. A careful investigation of the distribution of the boulder- 
matter has shown me, that whereas it has scarcely reached the high primary water-shed of 
Potter and IVPKeau counties, to enter the vaUeys of the Sinnemahoning or the other northern 
streams of the West Branch, it has been strewn much more freely over Bradford, Susquehanna, 
and Wayne counties on the east, and Warren, Crawford, and Elk on the west. In both of these 
districts the drift, as we shaU see hereafter, thins dow^n to a sheet of gravel, so shallow and 



38 



OROGRAPHY AND SCENERY OF FOURTH DISTRICT. 



sparse as scarcely to be discernible on the table-lands of Monroe and Lucerne, and of Butler and 
Lawrence. But while this is so, it is traceable much further south, in both these quarters, along 
the immediate river-valleys which extend from the plains of New York into or through the 
Appalachian Plateau. Though we discern the last or most southern sprinkling of it on the 
upland, no further south in the Appalachian Valley than Northampton and Lehigh counties, it is 
packed in a thick sheet, carved here and there into bold terraces, all the way down the valley of 
the Delaware to the level of the tide-water. And again in Western Pennsylvania, while it ceases 
on the hills in Mercer and Butler counties, it follows all the valleys which enter the Ohio Eiver 
from the north, not only those of the Alleghany and the Beaver rivers, but many more, debouching 
much further south in the State of Ohio. 

The prevalence of lakes and ponds within the drift-covered tracts of the country would appear 
to be connected with the partial blocking-up of the valleys and ravines by this material choking 
the outlets of the waters. It may be partly due, also, to the extreme levelness which it has 
imparted to the surface ; the original inequalities of the rocky floor of the country having been 
smoothed by the filling-up of the lesser depressions with this loose superficial coating. It has 
thus produced wide level plains in localities where, but for its presence, continuous irregular 
slopes would exist to drain away the waters in slender streams. In districts not covered with 
drift the water-sheds or summits separating the cliflerent systems of ravines and valleys are almost 
invariably too narrow to contain any large collections of water, as the opposite slopes are in close 
proximity. This is particularly true where the strata are anticlinal, or dip opposite ways from the 
summit, or even where they are monoclinal, or dip all in one direction. But in regions where 
the foundation-rocks of the country are overspread with a smooth mantle of drift, these water- 
sheds are apt to be extremely level plains, into which the lateral brooks descending from the 
hills collect and produce small lakes. Certain it is, that the most lake-bestudded districts of the 
United States and British territories of the continent are just those where these two conditions, 
namely, wide flat water-sheds and deep coverings of drift, prevail together. The Lacustrine 
tracts at the sources of the northern feeders of the St Lawrence and its Upper Lakes, but especially 
those at the sources of the Mississippi, where it interlocks with the waters of the St Lawrence and 
with those of Hudson Bay, are striking exemplifications of this general laAv. 

Other circumstances, however, besides the existence of the drift-stratum, conduce to the 
prevalence of lakes in the country N., N.E., and N.W. of Central Pennsylvania. From the 
Susquehanna Eiver south-westward, the strata of the Appalachian Chain and the Atlantic Slope 
are scarcely anywhere basin-shaped, or even flat in their dips over large areas ; but they undulate 
and incline at high angles. As a consequence, the ground above them slants in one or other 
direction too rapidly to support large tracts of still-water. But N.E. and N. of the Anthracite 
Coal-fields, and throughout Middle and Western New York, they incline very gently, and permit 
a far more frequent occurrence of horizontal plains or nearly level valleys, whose beds have been 
further smoothed by the introduction of the drift. The large lakes of Central New York evidently 
owe their origin to long transverse trenches or valleys, scooped out of the gently-south-dipping 
strata of that district, by the powerful force of a heavy sheet of moving water passing over the 
terraced surface of the State in a direction transverse to the outcrops of the rocks, or from N. to 
S. The softer formations have been excavated into long wide ravines, or great shallow valleys ; 
while the harder ones have been left at higher levels on the edges of the great terraces, contracting 



HYDROGKAPHY. 



39 



and partially closing the northern ends of these vast ravines. It is to the flattish southward dip 
of the strata, their alternation of hard and soft, and the transverse rush of the eroding currents, 
that we must ascribe the production of the basins of these beautiful sheets of water. 

GEOGRAPHY AND SCENERY OF THE FIFTH DISTRICT. 

After the descriptions already given of the other portions of Northern Pennsylvania, it is not 
necessary to dwell long upon the physical structure and aspect of that natural area which lies 
between the northern escarpments of the Lower Coal- rocks in Warren, Crawford, and Mercer, and 
the shore of Lake Erie. This is a somewhat diversified, undulated district, full of moderately deep 
ravines, intersecting and insulating innumerable low hills, which grow Hatter and tamer as we 
approach the water-shed, which traverses the belt longitudinally in a meandering course from 
New York to Ohio, at an average distance of 10 or 15 miles from the lake-shore. Between this 
water-shed or flat summit, dividing the streams flowing towards the Ohio River from those enter- 
ing Lake Erie, and the edge of the table-shaped hills, containing the lowest coal-rocks, the general 
surface, disregarding the local hills and hollows, is approximately a level plain. It is overstrewn 
with a thin sheet of drift, which is accumulated, however, in thicker masses, in terraces within 
its deeper valleys. This plain has a mean elevation above the sea of somewhere between 1100 
and 1200 feet. Owing to a combination of geological conditions already mentioned, namely, a 
fiat dip in the strata and a surface-covering of gravel or boulder-drift, it possesses several lakes 
near the sources of its streams. The largest of these is Cliatauque Lake, in New York, the surface 
of which is 1272 feet above tide- water. The chief lakes in Erie and Crawford counties are 
Oil-Creek Lake, Lake Pleasant, Leboeuf or Waterford Lake, Conneautte Lake, and Conneaut 
Lake. To these might be added Pymatuning Swamp, a long tract of wet, peaty marsh, covering 
the water-shed between Crooked Creek and an eastern tributary of Chenango Creek. 

The other much narrower division of the district — or that which lies between the water-shed 
of the Ohio and Lake streams and the shore of Lake Erie — -has a somewhat different configura- 
tion of its surface. It descends rather rapidly from the water-shed to the lake by a succession of 
obscure, alternately gentle and steepish slopes. The declination of the ground may be inferred 
from the difference in the elevation of its two margins ; that of the water-shed, in which it begins, 
being nearly 1200 feet, and that of the lake, in which it ends, being only 565 feet above the level 
of the sea. This tract is cut transversely by numerous sharp ravines and long tortuous valleys, 
carrying its waters to the lake ; and the borders of some of these afford many small, pleasing bits 
of scenery. But the characteristic, and altogether the most impressive pictures, are those of the 
lake itself. The first view which the traveller gets of this broad inland sea as he passes the 
water-shed, especially when the surface of the lake, crisped into gentle waves by a light western 
breeze, reflects the deep blue of the upper sky, never fails to charm and surprise him. 

HYDROGRAPHY. 

Turning our attention from the Orography of Pennsylvania, or the relief of its surface, to 
the Hydrography, or the features of its drainage, we perceive it to consist of three principal slopes, 
divided by two chief water-sheds — the Primary Appalachian Water-shed already traced, dividing 



40 



HYDROGRAPHY. 



the Atlantic streams from those of the Ohio Eiver, and the Lacustrine Water-shed, separating the 
latter from the tributaries of Lake Ontario and Lake Erie. 

The Great Hydrographic divisions and sub-divisions of the State may be appropriately classified 
in tabular form in the following manner : — 



Atlantic drainage flows into 



Basin of the Delaware Bay, whicli consists of the - 



Basin of the Chesapeake Bay, which embraces 



Mexican Gulf drainage flows into / Basin of the Ohio River, which includes in 

Pennsylvania 



Lake drainage flows into 



Basin of Lake Ontario in Pennsylvania, which 
embraces 

Basin of Lake Erie, embracing 



Basin of the Delaware River. 
„ Schuylkill „ 

„ Brandywine „ 

and a few other small streams. 

Basin of the Susquehanna. 

„ Potomac, — part only of 

which lies within the State. 

Basin of the Alleghany River. 
„ Beaver „ 

„ Monongahela „ 

and numerous lesser streams entering 
the Oliio River. 

Basin of the Genesee River at its 
source. 

j Conneaut Creek, and numerous short 
( streams. 



ATLANTIC DRAINAGE. 

Its general Periphery. — The Atlantic drainage of the State comprises about 28,526 square 
miles of its surface. The water-shed, enclosing the streams descending towards the Delaware 
and Chesapeake Bays, traced in its entire sweep round the sources of the Delaware and Susque- 
hanna in New York, is an irregular elliptical girdle ; it begins near the mouth of the Delaware 
Bay in New Jersey, ranges northward through that State to near its northern corner, thence north- 
ward into the Catskill Mountain, dividino; the drainage of the Delaware from that of the Hudson 
and of the Mohawk, and thence north-w^est ward along the Held erberg Mountain, between the streams 
of the Mohawk and those of the Susquehanna. Becoming now the primary water-shed, it turns 
to take a tortuous course south-westward between the waters of the North Branch of Susque- 
hanna and those of Lake Ontario, until in Potter County, Pennsylvania, it begins to di^dde those 
of the West Branch of Susquehanna from those of the Ohio Eiver, and continues thus southward 
to Cambria County, where it becomes the crest of the Alleghany Mountain, and separates the 
sources of the Juniata branch of the Susquehanna, from those of the Conemaugh of the Ohio 
Basin, Near the Maryland line, and in Maryland, this water-shed divides the head-streams of 
the Potomac from those of the Youghiogheny, another western water. 

Its chief River Basins and their dividing Water-sheds. — The waters of the Atlantic drain- 
age in Pennsylvania, belonging to the three large river-basins of the Delaware, Susquehanna, and 
Potomac, are separated into these receptacles by two important water-sheds, extending from the 
tide-water to the primary water-shed of the Appalachian Chain, or transversely to the mountains. 
That which insulates the streams of the Delaware, commences below Trenton, and extending 
north-westward through Bucks, Lehigh, and Schuylkill counties to the sources of the Catawissa, 



AREAS or THE CHIEF KIVER-BASINS. 



41 



there deflects northward through Lucerne, round the sources of the Lehigh, and thence through 
Wayne County, between the Delaware and the Susquehanna waters into New York. 

The other, which divides the waters of the Susquehanna from those of the Potomac and other 
streams entering the Chesapeake Bay, commences near Havre-de-Grace in Maryland, enters Penn- 
sylvania in the western corner of York County, runs thence north-westward to the Kittatinny 
Mountain in Franklin, and pursues an exceedingly tortuous course among the crests of the Appala- 
chian Ridges, through Franklin, Perry, Juniata, Huntingdon, Fulton, and Bedford counties, to a 
point where it meets the great primary water-shed of the State in the crest of the Alleghany, in the 
south-eastern corner of Somerset County. This is the southern boundary or rim of the Susque- 
hanna Basin ; its eastern boundary ranges from the head of the Chesapeake Bay northward through 
Chester, Berks, and Schuylkill counties to the sources of the Catawissa, where it falls into the water- 
shed confining the Delau^are Basin. Between it and the lower part of the Delaware water-shed 
lies the basin of the Schuylkill River, and also that of the Brandy wine, with one or two smaller 
ones, tributary to the Delaware and Chesapeake bays. 

A reas of the Chief River Basins. — The portion of the hydrographic basin of the Delaware 
River, lying within the State, contains about 3895 square miles of surface. It is a long 
comparatively narrow strip of country, widest in the middle, and stretches across the whole 
Mountain-zone of the State, from New York to the head of tide- water. 

The large division of the Susquehanna Basin belonging to Pennsylvania covers an area of 
not less than 17,018 square miles. It is much the largest of all the primary hydrographic 
basins of the State. 

The area of the Schuylkill Basin, carefully estimated, contains about 1884 square miles. 
This, which may be regarded as only a secondary basin of the Delaware River, extends from 
the tide-water into the mountains, but not across them, and does not span quite one-half of 
the breadth of the State. 

That part of the Potomac Basin which extends into Pennsylvania, occupying portions of 
Adams, Franklin, Fulton, Bedford, and Somerset counties, has a surface of about 1581 square 
miles. 

The small remaining area, tributary to the Atlantic tide-water, is the triangular basin of the 
Brandywine and its adjoining streams in Delaware and Chester counties. This we may estimate 
to cover not more than 720 square miles. 

The several chief river-basins of the Atlantic system here sketched, are in close hydro- 
graphic contact both with each other and with the exterior river-basins of the country. Their 
bounding and dividing water-sheds are in many places so depressed as to afibrd, especially in the 
valleys which they traverse, the most facile communication across them. One is astonished, 
indeed, to find by how many low summits, easily traversable b^ railroad and canal, they are con- 
nected with each other. Thus, however important a knowledge of these water-sheds or summit- 
lines of the drainage of the country is to the civil engineer in planning or constructing canals 
and other highways, they constitute no serious obstacle to free communication in all directions. 
They no doubt deflect the currents of inland trade, but it is only in a few districts that they can 
be said to arrest them. It is a fortunate feature in the Atlantic River Basins of Pennsylvania 
that they are thus connected, by wide frontiers and through singularly flat summits, with the two 
other great river-systems of the country, the Lake Basins in the north, and the great receptacle 

VOL. I. F 



42 



HYDROGKAPHY. 



of the Oliio drainage in the West. Thus Pennsylvania, though traversed nearly from end to end 
by a broad zone of mountains, is in-no way cut asunder by it. On the contrary, its river- valleys 
rather link its distant parts together, and by their stretching beyond its borders into the neigh- 
bouring States, open channels to a wide external commerce. 

Mexican Gulf, or Ohio River Drainage. — The large river-basin of the Ohio- Alleghany River, 
comprising all that district which lies west of the Primary Water-shed of the State, excepting 
merely the narrow strip composing the Lake Erie slope, contains, upon a careful estimate, about 
12,632 square miles of surface. From a mean elevation above the sea in its north-eastern and 
south-eastern corners of about 1800 feet, it falls towards the Ohio River to a level of about 1000 
feet, and in the beds of the streams to about 700 feet. This river-basin has on its N.E. that of 
the Genesee, and on its E. those of the Susquehanna, the Juniata, and the Potomac. On its N.W. 
it is separated by a very easily passed water-shed from the Basin of Lake Erie. 

The Basin of the Juniata River, by far the largest tributary of the main Susquehanna below 
its two northern branches, covers a surface of about 3428 square miles. By this basin and 
that of the West Branch, the Susquehanna River expands itself entirely across the mountains, 
spreading to a far greater distance westward than it does eastward. The North Branch, however, 
which must be regarded as the main stream — the others being affluents — has its area of greatest 
expansion towards the north, where in New York it waters a wide extent of country. 

The Pennsylvanian portion of the basin of the Ohio River is divisible into three sub-basins 
of drainage — that of the Alleghany River, that of the Monongahela, and that of the Beaver 
River. The hydrographic valley of the Alleghany River within Pennsylvania occupies an area 
of about 9546 square miles. The portion of the Monongahela Basin included within our 
borders covers the less space of 2800 square miles. The district, drained by streams entering 
the Ohio directly, including that part of the Beaver River Valley which belongs to our territory, 
may be assumed to contain about 3086 square miles. 

The Lake Drainage. — A very small area of the Genesee Basin of Lake Ontario enters 
Pennsylvania ; it probably contains not more than 90 square miles. 

The Lake Erie Slope, occupying a part of Erie and a small portion of Crawford counties, 
may be estimated to cover about 352 square miles. It is very difficult, in the absence of a perfect 
map of the streams of Pennsylvania, to reach exactitude in the estimation of the areas occupied 
by these several river-systems and their subdivisions. 



THE DELAWARE 



RIVER-SYSTEM OF THE DELAWARE RIVER. 



43 



' Has its source in the N.E. corner of Delaware County, at an elevation of about 2000 feet above the sea. 
It traverses Dehiware County, New York, flows between Pennsylvania and New York as far as Carpenter's 
Point, thence between Pennsylvania and New Jersey as tar as the State-line below Chester, and thence 
between the State of Delaware and New Jersey to its estuary the Delaware Bay. 



THE 
DELAWARE 



the Lackawanna Creek, 



the Lehigh River, 



from the ri(/ht 



It / 

receives \ 



the Schuylkill River, 



\ from the left 



the Pawpactou, 



the Neversink River, 



several large streams in 



which rises in JVToosick Mountain, on the Eastern bor- 
ders of Wayne Couuty, and flows Eastward through 
Wayne and Pike. 

The towns washed by it and its branches are — Belmont, 
Mount Pleasant, Bethany, Honesdale, and Hawley. 

It empties into the Delaware between Mount Hope and 
Barry ville. 

which rises in the table-land of the Pokono Mountains, 
in the swamps called the " Shades of Death," in Mon- 
roe and Lucerne counties. 

It traverses thence between Lucerne and Carbon, and 
across the latter, and between Lehigh and Northamp- 
ton, and through tlie latter. 

The towns seated on or near it and its branches are 
— Stoddartsville, Whitehaven, Pennhaven, Mauch 
Chunk, Lehighton, Wcissport, Parryville, Allentown, 
Bethlehem, and Easton. 

^It empties into the Delaware just below Easton. 

which rises in the Southern Anthracite Coal-field in 
Schuylkill County. 

It traverses Schuylkill, Berks, Montgomery, and Phila- 
delphia counties, flowing towards the S.E. 

The towns seated on or near it are — Tuscarora, Middle- 
port, Port Carbon, Pottsville, Schuylkill Haven, Or- 
wigsburg,Port-Clinton,Hambiu-g,Reading,Pottstown, 
Plicenixville, Norristown, Mauayunk, and Phila- 
delphia. 

on the ri(/ht from Broad Mountain— Mill 
Creek, West Branch, Tulpehocken, and 
French Cr. 
on the left -fi-om Broad Moimtain — Little 
Schuylkill, Maiden Cr., Manatawny, 
Perkiomeu, and Wissahickou ; 
and empties into the tidal portion of the Delaware a 
^ few miles below Philadelphia. 

which rises in the plateau of the Catskill Mountain ; 
traverses Delaware County, N. York, flowing westward ; 
and empties into the Delaware at Hancock. 

I which rises in the North part of Ulster County ; 
traverses Ulster and Sullivan, flowing southward. 
The chief town seated on or near it is Montecello. 
It empties into the Delaware at Carpenter's Point, 
. below Port Jarvis. 

which rises in Monmouth and Burlington counties. New 
J ersey ; 



It i'eceives 



and traverses Burlington County. 



New Jersey, the chief of ( Its totvns are. — Pemberton, Mount HoUey, Vincent-town, 



which is the Raucocos, 



Eayrstowu, Lumberton, &c. 
It e?H ^j^iiVs into the Delaware a few miles below Biu"- 
lington City. 



It 2^etsses by or near the towns of Narrowsburg and Port Jarvis in New York ; ]\Iilford in Pennsylvania ; 
Belvidere in New Jersey ; Easton and New Hope in Pennsylvania ; Trenton, Bordentown, and Burling- 
ton in New Jersey ; Philadelphia and Chester in Pennsylvania ; and Wilmington in Delaware. 
^It empties into the Delaware Bay. 



44 



HYDROGRAPHY. 



THE 



tlie Shenango River, 



the Chemung Kiver, 



the Great West Branch 
of the Susquehanna, its 
rival in size, 



''from the right, ^ 



SUSQUEHANNA 



rives \ 



It 

receive 



the Juniata River, " 



Bises in Otsego County, New York, in and near Otsego Lake, on an elevated table-land. 
It traverses Otsego, Broome, and 'Tioga counties, in New York, and entering Pennsylvania in Bradford County, 
passes through it and Wyoming, Luzerne, Columbia, Montour, and Northumberland, and flows between the 
last and Snyder, and between Dauphin and Perry, and Cumberland, and thence between Lancaster and York 
to Maryland, where it presently enters the head of the Chesapeake Bay. 

i which rises in Madison County, New York ; 
I traverses Shenango and Broome counties, N. Y. ; 
I loashes the towns of Sherburne and Norwich ; 
, and empties into the Susquehanna at Bingham pton in N. Y. 
' which rises in Stenben County, N. Y. ; 
I trarerses Steuben and Chemung counties, N. Y. ; 
1 washes the towns of Bath and Elmira ; 
^ and empties into Susq., below Athens, 
'^which r/Mfs in Cambria County, Pennsylvania ; 
trarrrxrs Clearfield, Clinton, and Lycoming, and divides 
Union from part of Northumberland to its junction with 
the North Branch of the Main Susq. ; 
■washes the towns of Clearfield, Lockpoi-t, Jesseyshore, 
\Villiamsport, Muncy, Milton, Lewisburg, and Northum- 
berland ; 

and empties into the Susq. at Northumberland ; 

■ from the rif/ht — Clearfield Cr , Mushannon 
Cr., Bald Eagle Cr., Whitedeer-hole Cr., Buf- 
falo Cr., and several lesser ones ; 
from the left — the Siunemahoning Cr., Kettle 
Cr., Pine Cr., Lycoming Cr., Loyalsock Cr., 
Muncy Cr., ChiJiisquaque Cr., and several 
V ^ lesser ones. 

which rises on the Eastern slope of the Alleghany Moun- 
tain in Blair and Bedford counties ; 
traverses Bedford, Huntingdon, Mifflin, Juniata, and Perry 
counties ; 

passes the towns of Bedford, Huntingdon, Newton Hamil- 
ton, Lewistown, Mifflintown, and MiUerstown ; 
and empties into the Susq. at Duncan's Island, above 

Petersburg ; 

'from the right — Trough Cr., Aughwick Cr., 
Tuscarora Cr., Buffalo Cr., and several lesser 
It / ones ; 
receives \ from the left — Frankstown Cr., Kishicoquil- 
las Cr., Cocolamus Cr., and several lesser 
ones. 

I such as Cayuga River, Sugar Cr., Tawanda Cr., Mahoo- 
1 . peny Cr., Fishing Cr., Penn's Cr., Sherman's Cr., C'one- 
I dogwinit Cr., Yellow Breeches Cr., Conewago Cr., 
' Codorus Cr., and Deer Cr. 

r which rises on the border of Wayne and Susquehanna 
I counties ; 

>. traverses part of Susquehanna and Luzerne Counties ; 

fiasses by Carbondale, Scranton, and Pittston ; 
[and empties into the Susq. at Pittston. 

which rises in Schuylkill Coimty in the Southern Coal 
Basin ; 

tran-rses the Western part of Schuylkill, also Lebanon and 

t Dauphin counties ; 
passes the towns of Tremont, Pinegrove, and Humel's 
Town ; 
and empties into the Susq. at Middletown. 

Twhich rises in the Southern corner of Berks County, on 
I the border of Chester ; 
/ trarerses Lancaster County; 

\ passes Morgantown, Churchtown, Lancaster, and Safe 
I Harbour ; 

vand empties into the Susq., near Safe Harbom-. 

I which rises near the Eastern side of Lancaster Coimty, 
I South of the Copper Mine Ridge ; 

< trarerses the Southern part of Lancaster County, and a 
I small part of Cecil County, Maryland ; 
I and empties into the Susq. a few miles above Port Deposit. 

( such as the Wyalusing Cr., Tvinkhannock Cr., Nescopeck 
\ Cr., Catawissa Cr., Shamokiu Cr., Mahanoy Cr., Mahan- 
) tanga Cr., Wiconisco Cr., Chiques Cr., and Conewiugo 
( Cr. 

It passes by or near the towns of Unadilla, Great Bend, Binghampton, Owego, Athens, Tawanda, Tunkhannock, 
Pittston, Wilkesbarre, Berwick, Bloomsburg, Danville, Northumberland, Sunbury, Dauphin, Harrisburg, 
Marietta, Columbia, Port Deposit, and Havre-de-Grace. 



also numerous second- 
rate, but important 
^streams. 



the Lackawanna Creek, 



the Swatara Creek, 



from the left, <^ 



the Connestoga Creek, 



and Octorara Creek, 



besides many smaller 
ones, 



It empties into the Chesapeake Bay in Maiyland, about 12 miles ."louth of the State line of Pennsylvania. 



RIVER- SYSTEM OF THE POTOMAC RIVER. 



45 



Rises in Hardy County, Virginia, at an elevation of about 2500 feet above the sea. 

It traverses Hardy County, "N^irginia, and Allegliaiiy County, Maryhiud, and flows thence Eastward 
and South-eastward, between Maryland and Virginia, the whole way to its entrance into Chesa- 
peake Bay. 



/^from the ri ht I rivers and important second-class streams, which, belonging wholly 

( to Virginia, need not be here described. 



C no important river, but several large streams, called " Creeks," namely- 



THE 
POTOMAC 



It J 

receives \ 



) 



from the left < 



WiUs' Creek, 



Town Cr., 



Sideling-hill Cr., 



Licking Cr. 



Conecocheague Cr. 



r which rises in Somerset County, at the East base of the 
Alleghany Mountain ; 
traverses the South-east corner of Somerset, North-west 
corner of Bedford, and the narrow part of Maryland ; 
2Xisses no important town ; 
and emjyties into the Potomac at Cumberland. 

(which 7'ises on the East slope of Tussey Mountain, in 
the South part of Bedford County ; 
and empties into the Potomac below Old Town. 

which rises in the valley West of Townhill, in the South- 
east corner of Bedford ; 

and eynpties into the Potomac above the mouth of the 
Cacapon River. 



f which rises in Fulton County, East of M°ConuelIstown 
Cove; 
and empties into the Potomac several miles East of 
Hancock. 

(which rises in Franklin County in Anderson's Valley 
—East Branch rises in the North-west corner of 
Adams' county ; 
and empties into the Potomac at Williamsburg. 



All these streams traverse the narrow part of Maryland, after flowing out 
of Pennsylvania. 



THE ALLEGHANY 



46 



HYDROGRAPHY. 



THE 
ALLEGHANY 



the Conewango Creek, 



the French Creek, 



the Beaver River, 



Jxises near the centre of Potter County, at an elevation of about 1700 feet above the sea. 

It traverses the west part of Potter, N.E. corner of M'-Kean, then enters New York, and returns into Pennsylvania in the 
N.E. corner of Warren County, which it traverses diagonally, and passes through Venango, Clarion, and Aimstrong, 
and between Butler and Alleghany, where, at Pittsburg, it drops its name and takes that of the Ohio, passing between 
Butler and the rest of Alleghany County, and then across Beaver County, to become the dividing limit between the 
States of Ohio and Virginia. 

/ which rises in Cattaraugus County, New York; 
j traverses Cattaraugus County, New York, and the North part of 
J Warren County, Pennsylvania; 
\empties at Warren into the Alleghany. 

r which rises in Chatauque County, New York, not far from Cha- 
I tauque Lake; 

j traverses the S.W. comer of Chatauque County, New York, 
and Erie, Crawford, and part of Venango comities, Penn- 
sylvania; 

passes at or near the town of Meadville ; 
and empties into the Alleghany at Franklin. 

which rises under the name of Chenango, the main Pennsylvanian 
stem, in the N.W. corner of Crawford County, West of Con- 
neautville ; 

from the rijh t, iraiYcje^ West sides of Crawford, Mercer, Lawrence, and Northern 

half of Beaver counties ; 
jjasses at or near the towns of Lawrence, Newcastle, Sharon, and 
Greenville ; 

from the rir/ht— the Mahoning River, which rises in the 
Lake Water-shed in Ohio, traverses Summit, Portage, 
Warren, and Mahoning counties of that State, and 
emjities into the Beaver or Chenango in Lawrence 
It County, below Newcastle ; 

receives ^ from the left — Neshannock Creek, which (rai-mei Mercer 
County, and empties into it below Newcastle and 
Slippery-rock Creek, which ti-averses Butler, a part 
of Lawrence, and empties into the Beaver near the 
North line of Beaver County ; 
and empties into the Alleghany at Beaver. 

which rises in Warren County ; 

traverses the S.E. portion of Warren, and Eastern part of Ven- 
ango Counties ; 
and empties into the Alleghany at Tionesta. 

i which rises in the South part of M'-Kean County, at an elevation 
of nearly 2000 feet ; 
/ traverses Elk, S. edge of Forest, and middle of Clarion counties ; 
\ passes at or near the towns of Ridgeway and Clarion ; * 
(,and empties into the Alleghany at Foxburg. 

I which rises in the Western border of Cleai-field County ; 
' traverses centre of Jefferson and Northern border of Armstrong 
counties ; 

I passes at or near the town of Brookville ; 
' and empties into the Alleghany near Vanburen. 

I which rises in the Western border of Clearfield County ; 
traverses Southern side of Jefferson, and Northern side of Arm- 
strong counties ; 
passes at or near the lomns of Punxatawney and Nicholsburgh ; 
and empties into the Alleghany some miles above Kittanning. 

which rises in the interior of Indiana County ; 

West part of Indiana, and Eastern half of Armstrong ; 
ies several miles below Kittanning. 
which rises in the Eastern border of Cambrian County, in the 

Alleghany Mountain ; 
traverses the breadth of Cambria County, and the whole Northern 
border of Westmoreland ; 

of Johnstown, Bolivar, Blairsville, Salts- 



It 

receives \ 



f the Tionesta Creek, 



the Clarion River, 



the Red-bank Creek, 



the Mahoning Creek, 



the Crooked Creek, 



I 

from the left, 



the Conemaugh, or 
Kiskiminetas River, 



( which rise. 
< traverses \' 
( and emptie 

! 

I passes at or near the towns c 
I burg, and Leechburg ; 
'-and empties into the Allegh 



the Monongahela River, 



ipties into the Alleghany at Freeport. 
which rises in Virginia, in Lewis County ; 

traverses Lewis, Harrison, and Monongalia counties in Virginia, 
and divides Kavette and Westmoreland from Green and Wash- 
ington, North of which it travei-ses Alleghany County to Pitts- 
burg ; 

passes at or near the towns of Morgantown, Greensburg, Browns- 
villo, Willianisport, Elizabethtown, and SI'-'Kee's Port ; 
'n reeeifes fi cm the ri>//it the Cheat River, which rises in Vii^inia iu 
the backbone of the Alleghany Mountain, and empties into it a 
short distance North of the Stateline, and the Youghioghenj', 
which rises in the Backbone Jlountain, traverses Hampshire 
county, Virginia, northward, and Somei-set, Fayette, and AUe- 
glmny counties, Pennsylvania, north-westward, emptying into 
it at -M'^lvee's Port ; 
and empties into the Alleghany at Pittsburg. 

which rises in the centre of Washington County ; 
traverses the Northern half of Washington, and Southern half of 

Alleghany Counties ; 
passes at or near the toivn of Washington ; 
and empties into the Alleghany three miles below Pittsbm-g. 

It passes by or near the towns of Couderspurt. Clean, Warren, Franklin, Kittanning, Freeport, Pittsbui^, and Beaver; _ 
It empties, or more properly, it chan-cs it. iv.aur at Pittsburg into the Ohio River, which empties into the Mississippi 
River at Cairo, the Suuthern point of the State of Illinois. 



the Chartiers Creek, 



v 



RIVER SCENERY. 



47 



SCENERY ALONG THE PRINCIPAL RIVERS. 

The Delaware River. — This noble river, the eastern boundary of Pennsylvania, throughout 
its entire breadth exhibits, along its immediate valley, a considerable variety of topographical 
feature and scenery. From its head-streams in New York, to where it emerges from the Pokono 
or Catskill Mountain, it flows in a tortuous course through a deep narrow trough in that elevated 
table-land. The mean level of the plateau remaining nearly constant, and the valley growing pro- 
gressively deeper, the river-hills, which are all that the traveller at the river-side usually beholds, 
grow higher and steeper as he descends. Meandering much more than the valley containing it, 
the river sweeps sometimes close by the base of the bounding hills, the lower parts of which are, 
in many cases, faced by high naked cliffs, exposing the reddish brown shales and sandstones of 
the district, in beautiful contrast with the mixed green hues of the foliage. The perspective of 
jutting and retreating hills, clothed for the most part with a combination of coniferous and decid- 
uous forest to their summits, and washed at their base by long bending reaches of the broad river, 
are very attractive, notwithstanding a prevailing sameness in general feature. After leaving the 
plateau in Pike and Wayne counties, the river emerges into a broad open valley, wholly different 
in aspect and structure from that which it has left. The waters which carved a way for it seem 
to have been impelled in their momentum southward, with great energy, against the strong stony 
barrier of the Kittatinny or Shawangunk Mountain, and to have scooped their deepest trench 
near the base of that high ridge. The river, therefore, turns abruptly at Carpenter's Point, from 
a S.E. to a S.W. course, and follows the foot of the mountain, sometimes hugging its base, some- 
times sweeping a moderate distance from it into the plain, until it finds a passage through it 
by the great breach called the Delaware Water-gap. The scenery along this stretch of the river 
is eminently beautiful. Low within the valley, the river is bordered by fertile cultivated flats, 
variously carved in one or more terraces ; and behind these, particularly on the N.W., rise numer- 
ous rolling hills, some under, the plough, some covered with timber, all deeply cut by ravines, 
in the steeper of which are many beautiful waterfalls, while still beyond the hills we see ascend- 
ing the long slopes or bold escarpments of the plateau of the Upper Delaware. All the way 
along on our left the view is bounded by the forest-covered flank and straight crest of the Kitta- 
tinny Mountain. 

Turning at the Water-gap, the Delaware, in issuing through the main ridge of the mountain, 
passes between steep, nearly perpendicular, mural cliffs of grey sandstone, rising on either side 
to its very crest. The sketch of this scene from the S. will give some notion of its character. 

Leaving the Water-gap, the river descends gently southward, obliquely across the entire 
Ijreadth of the Appalacliian Plain or Valley, to where it enters the hills called " The South 
Mountains," below Easton. This portion of its course is marked by no striking features, the 
surface of the country being elevated only 100 or 200 feet above it, and being, from the softness 
of the slates and limestones, smoothed down into rather inexpressive lines. 

Below the mouth of the Lehigh, the Delaware is bordered by an alternation of hills and 
narrow intervening valleys, the river-hills being but the ends of the intersected ridges of the low 
chain of the Highlands of New Jersey ; but from the southern edge of these hills, at Durham, the 
scenery for many miles southward wears a wholly different character. It is that of a table-land, 



48 



HYDROGRAPHY. 



elevated 300 or 400 feet above the level of the river, cut on one or both sides of the valley into 
long ranges of perpendicular precipices, or extremely steep slopes. One stretch of precipice on 
the Pennsylvania side, known by the name of the Nockamixon Eocks, is an exceedingly striking 
and picturesque range of beetling cliffs, rising sheer for 200 or 300 feet from the brink of the 
river, with only a narrow roadway between them, through a length of nearly 3 miles. Some 
of the views from the base of these crags are almost grand ; and the pictures they make with 
the river below are beautiful. Tufts of bushes and trees, and climbing vines, heighten by their 
green hues the rich brown tints of the rocks, to tlie bold faces and narrow ledges of which they 
lend a grace which no cliffs without A^egetation ever possess. There are few more attractive 
drives or walks by the river borders of Pennsylvania than this one at the foot of the Nocka- 
mixon Rocks. 

Further down its valley the Delaware passes, in the vicinity of New Hope, some bold ridges 
of trap-rock, which impart a pleasing variety to banks, elsewhere, in this part of its course, 
comparatively tame. Passing Trenton, its borders presently put on a totally changed aspect. 
Ceasing to be a gay running stream, full of bushy islands, and rocky reefs, and rapids, it becomes 
a w^ide tidal river, rising and ebbing between shores which are in many places only low banks of 
sand and gravel, and in others, broad slimy marshes, covered with reeds and grass. Turning at 
Bordentown south-westward, the river maintains these features all the way to its wide estuary, 
the Delaware Bay. 

The Susquehanna River — North Branch. — That portion of the Susquehanna River which 
flows near the northern boundary of the State, passes from its sharp elbow, called " The Great 
Bend," to the mouth of its affluent, the Chemung River, throuo-h a charmino; broad vallev, 
bounded by soft slopes, terminating in wide table-shaped hills. It is a fertile and very beautiful 
district : and with its westward extension, the plain of the Chemung River is rapidly becom- 
ing one of the most attractive agricultural districts of New York. From the mouth of the 
Chemung River to Pittston, where the river suddenly turns at a right angle on entering the 
Wyoming Coal-field, it flows, with many bendings, along a deep and picturesque valley, almost 
identical in its features with that of the corresponding sketch of the Delaware, the main differ- 
ence being, that the bed of the valley is wider, and the hill-sides confining it less mountainous. 
From the mouth of the Lackawanna at Pittston, where it enters, to Nanticoke, where it leaves the 
beautiful Wyoming Valley, the scenery along the river is wholly different. It flows through a 
broad and almost perfectly level smooth plain — the Wyoming and Kingston Flats — composed 
of a deep bed of diluvium or drift. On either side of this plain rise the rolhng hiUs of the coal- 
basin, and behind these the long gentle slopes of the high mountain-barriers which frame in the 
whole scene. At Nanticoke the river turns abruptly northward out of the coal-basin, through 
its steep barrier, by a highly picturesque pass, and then sweeps again as suddenly westward, to 
run for several miles in a closely-confined trench, between the outer and the inner ridges of the 
basin. It does not, however, run round the western end of this, but at the ravine of the Shick- 
shinny turns suddenly southward, and cuts across its point, leaving a high insulated hill of the 
coal strata on its western or right-hand side. Disengaging itself by a fine pass from the southern 
barrier of the coal-basin, it passes out into an open valley, and makes another rectangular bend, 
to run once more towards the W., parallel with the Nescopeck Mountain, which it follows to the 
neighbourhood of Catawissa. Beyond this point it maintains its general com-se westward, some- 



SUSQUEHANNA RIVER 



49 



what S., parallel with the southern base of Montour's Eidge, all the way to Northumberland, 
where it is joined by its great tributary, the West Branch. In some portions of this long reach 
of the river, the scenery adjoining it is uncommonly rich and pleasing. A remarkably fine view 
up the river is presented from the hills on its west bank, a little below the mouth, of Fishing 
Creek. 

Between Northumberland and the Kittatinny Valley the river leads us through many strik- 
ing scenes. It is studded with many little islands, most of which are covered with trees or 
bushes to the water's edge ; and it is here a wide and majestic river, flowing alternately for long 
reaches, across highly cultivated belts of country, and past the ends of steep and rugged moun- 
tains. (The View of the river at the gap of the second mountain will convey some notion of the 
appearance of its banks.) (The Scene, embracing the Blue Hill at Northumberland shows the 
junction of the North and West Branches, and gives a just conception of the style of the hills 
bounding its immediate valley.) Passing out from the mountains, it traverses a beautiful 
country in the Kittatinny Valley, dividing Dauphin from Cumberland County. There are superl:) 
views of this reach of the river from Harrisburg, from the dome of the Capitol, and also from 
the southern slope or summit of the Blue or Kittatinny Mountain ; and again from the high hiUs 
on the edge of York County. Quitting the Limestone VaUey, the river next traverses the Red- 
shale Belt, between the villages of Highspire and Bainbridge, crossing a rather monotonous 
country, except at the Conewango Falls, or Rapids, where numerous hard trap-dykes impede, its 
course, and cause it to rush in wild tumult, by deep and dangerous sluices, for a long distance 
between black and jutting reefs. At Chiques Ridge, one mile above Columbia, the river leaves 
tlie smoother country, and passes between a range of high and picturesque crags. With two or 
three intermissions, caused by the softer limestone valleys which it next crosses, it runs the 
whole way thence to the vicinity of Port Deposit, or nearly to the head of the Chesapeake Bay, 
between steep, naked, and half-naked hill-sides, rising from 200 to 400 feet above its channel. 
In some parts of this long reach, as at the mouth of the Conestoga, the river is greatly dilated, 
and is filled with rocky islands and projecting reefs. In other localities its rugged banks 
approach, and the river rushes with tremendous force, especially during freshets, through these 
deeper gorges. The traveller, who finds only a rough and very toilsome path along its eastern 
shore, from Turkey Hill to Port Deposit, a distance of more than thirty miles, will choose to 
descend it by its right bank along the tow-path of the Canal. He will pass an almost unbroken 
succession of interesting rocky scenes, aSbrding much geological instruction ; and he will witness 
many beautiful bits of river perspective, but he will find himself pent in all the way between the 
bold river-hills. 

West Branch of Susquehanna. — The upper part of the West Branch of the Susquehanna, 
and also its tributaries, the Sinnemahoning, Kettle Creek, Pine Creek, &c., draining the high 
plateau N.W. of the Alleghany Mountain, flow through deep trenches in the horizontal strata, very 
analogous in their features to those which give passage to the Delaware, and the Main, or North 
Susquehanna, in the north-eastern part of the State. From the mouth of the Sinnemahoning, 
out into the Bald Eagle Valley, the river-hills are very high and steep, and admit extremely 
narrow strips of level ground between their feet and the river, except near the openings of the 
lateral streams. The trough through which the lower half of Pine Creek flows is equally pro- 
found. A notion of the appearance of this high table-land, where the larger streams intersect 

VOL. I. G 



50 HYDROGRAPHY. 

it to its base, may be gleaned from the little outline Sketch, showing the hills near Young 
Woman's Creek. 

Entering the valley between the Alleghany Mountain and the Bald Eagle Eidge, the river 
pursues a beautiful winding-course the whole way from Lock Haven to the neighbourhood of 
Muncy, alternately sweeping towards the middle of the cultivated valley and back again, close 
into the.base of the steep and' wood-covered ridge. Near Muncy it turns with a broad majestic 
curve round the end of the Bald Eagle Mountain, and in a few miles deflects from a S.\V. to a 
S. course, through a highly fertile, richly cultivated, open country, till it strikes the base of the 
Blue Hill, or range of Eed Sandstone Cliff's above Northumberland. S.W. of Muncy the river 
crosses a singular belt of deeply-eroded country, full of conical hills. Our Picture (see Plate) 
represents these Muncy Hills, the river, and the point of the Whitedeer Mountain. All this 
lower reach of the West Branch abounds in charming scenery, if the observer is at the pains to 
ascend one of the mountain-spurs or hills, high enough to open sufficiently expansive views. 

The Jimiata River.- — This second great tributary of the Susquehanna has two chief upper 
divisions, the Frankstown and the Kaystown Branches, both of which, like the main stream below 
their junction, traverse much beautiful scenery. We will trace the Frankstown Branch as that 
which is most accessible. After gathering its head- waters from the eastern slope, and the foot- 
hills of the Alleghany Mountain, it begins to assume the volume of a small river near Frankstown. 
Below this point it first passes the Cove of the Lock Mountain, a curious district of conical hills, 
in structure very like the Muncy Hills of the West Branch. Its course is now by a wild and 
rocky gorge through the Lock or Canoe Mountain, into Canoe Valley. Winding north-eastward 
through this valley, it next goes through Tussey Mountain into Hartslog Valley by an interesting 
curving pass of the form of the letter S. The mountain, which consists of two ridges, is trenched 
along its centre for the passage of the river, and the western ridge is moreover breached at Water 
Street by a lateral notch, which gives passage to a small tributary stream, and heightens much 
the picturesqueness of the place, which is farther enhanced by a great stone-slide covering the 
ends of the mountain. Crossing Hartslog Valley, it next traverses Warrior Ridge, passing by 
the Pulpit Pocks, one view of which is exhibited in the frontispiece to this volume. Emerging 
from the Warrior Pidge, and deflecting more towards the east, it crosses the Huntingdon Valley 
and passes by the northern end or knob of Terrace Mountain and Sideling Hill, receiving first the 
Raystown Branch, which nearly doubles the volume of its waters. Here bending southward, it 
follows a picturesque gap through Stone Ridge — a sketch of which, at the Canal, is given in this 
work — and turning more eastward, it presently enters the deep cleft in Jack's Mountain, called 
" Jack's Narrows," upon the western side of which the mountain is covered with a great stone-slide, 
or field of naked angidar blocks of sandstone, which imparts a most desolate aspect to the pass, 
especially when the forest is not in leaf. On emerging from Jack's Narrows, the river crosses a 
succession of open valleys divided by narrow ridges, until it meets the base of Blue Ridge in 
Sugar Valley. There it makes a great loop, turning in an ox-bow backward, till it reaches 
Newton Hamilton, whence it flows with many large sinuosities, longitudinally, through the Juniata 
or Levvistown Valley, to the deep synclinal ravine called the " Long Narrows," formed by the 
near approach of the Blue and Shade Mountains. 

The Picture of the Lewistown Valley, as it appears from the ridge west of Lewisto-vvn, which 
is given in this work, will sufficiently exhibit the character of its scenery. 



ALLEGHANY RIVEK. 



51 



The LoEg Narrows of the Juniata is a narrow trough between mountain-ridges, deeply 
trenched on their flanks, and thickly clothed with timber on their lower slopes and at their base, 
and overspread nearer their summits with extensive sloping sheets of dark-grey angular blocks. 
The pass is seven miles long, and is one of the wildest and most impressive within the mountains. 
At the eastern end of the Long Narrows, the river turns south-eastward, and winds between hills 
and valleys across the country, to the base of the Tuscarora Mountain, passing Mifflintown, Mexico, 
and other villao;es. This is one of its most beautiful districts : but the finest views are not imme- 
diately upon the river, but from the higher hills which overlook it at a moderate distance. Below 
New Mexico it sweeps the base of the Tuscarora Mountain for several miles, until it turns abruptly 
across its eastern end, a mile N.W. of Millerstown. The pass by which it traverses the end of 
the mountain is a simple notch, much less grand than some of the other water-gaps ; but the long 
straight reach of the river, before it enters the notch, furnishes a fine view of the beautifully sym- 
metrical form of the Tuscarora Mountain stretching for a great distance. Below Millerstown the 
river crosses the Wildcat and Buff"alo Valleys, washing the end of the Buffalo Mountain. We get 
superb views of the terminal knob of this ridge, which in shape is like the curving hump and 
neck of the Bison that once frequented the region, with the river and its tree-covered banks in 
the foreground. Pursuing its course, the Juniata, after making two or three bends, goes through 
a belt of hills called the " Half-fall Mountain," where, as at nearly all its passes through the larger 
sandstone ridges, it is impeded by ledges of hard strata, and thrown into ripples or rapids. From 
the Half-fall Eapids it flows between steep but low cliffs and hills, for about four miles further, to 
its entrance into the main Juniata, at Duncan's Island, having followed a winding course entirely 
across the central zone of the Appalachian Chain, through a distance of nearly 200 miles. 



THE ALLEGHANY EIVEE. 



I shall complete this sketch of the chief rivers of Pennsylvania with a concise description of 
the Alleghany, but shall omit any specific account of its local scenery, as the topographical and 
pictorial features of the wide region watered by it, and by its tributaries, have been already sufli- 
ciently delineated. 

The Alleghany, from its sources to where it becomes the Ohio Eiver, flows through a deep 
and comparatively narrow trench, excavated in the north-western plateau, and western coal-basin 
of the State. From the centre of Potter County, where it takes its rise, it runs with a somewhat 
swift descent westward, and then northward in a curving course, till it enters New York. There 
it takes a wide sweep north-westward into Cattaraugus County, passing Glean, to pursue from near 
Valley Creek a long sinuous south-westward course, to its great bend at Franklin. Edging its 
way gradually into the coal-basin, the north-western margin of which it enters near Warren, it 
takes an abrupt turn at the mouth of French Creek, and runs across the coal-field south-eastward 
to the mouth of the Mahoning, traversing entirely the sixth or last sub-basin, and entering the 
fifth or that of Brookville and Kittanning. Near the mouth of the Mahoning, the Eiver Valley 
suddenly departs from its previous south-eastward trend, to resume its normal S.W. direction, or 
to follow the length of the coal-basin. This it does by a succession of convex and concave sweeps 
to Pittsburg, where, upon receiving its noble tributary, the Monongaliela Eiver, it deflects north- 



52 



CLIMATOLOGY. 



westward at right angles, and stretches to the mouth of the Beaver River, where it makes another 
rectangular elbow, flexing to the S.W. to leave Pennsylvania, and pass into the State of Ohio. 

A little attention to the relations of the present drainage of the country, to the general 
scooping of the surface by the primeval waters which shaped it, will show us why the Alleghany 
River assumes the remarkable rectangular changes of direction which we have above noted ; 
first flowing S.W. ; thence from French Creek to Mahoning south-eastward ; thence to Pittsburg 
south-westward again ; thence to Beaver north-westward ; and once more from Beaver south- 
westward into Ohio. It is evident that, while the main discharge of the denuding wave was 
south-westward, or down the broad trough of the bituminous coal-field, one large influx of 
eroding waters swept the basin north-westward from the Appalachian ]\Iountains, and another 
south-eastward from the region of the lakes. Thus it has arisen that all this western district of 
Pennsylvania is trenched by three main systems of valleys, as respects their directions ; chief 
valleys stretching south-westward, other valleys opening into these at right-angles, or north- 
westward and northward, and a third set also opening at right-angles into the same first system 
south-eastward and southward. 

The streams of the north-western slope, or those draining into Lake Erie, are relatively too 
insignificant to merit here the kind of description called for by the Delaware, Susquehanna, 
Juniata, and Alleghany Rivers. We pass, therefore, now to a brief sketch of the Climatology of 
the State. 

CLIMATOLOGY OF PENNSYLVANIA. 

As respects its climate, Pennsylvania is very fortunately related to the rest of the United 
States. Owing to its midway station in the Appalachian Chain, between the cold region of the 
Gulf of St Lawrence and the tropical heats of the Gulf of Mexico, it enjoys, in point of tempe- 
rature, a climate nearer to the medium of that of the whole country than any other district on 
the Atlantic side. This temperate condition is also partly due to the softening influence of 
proximity to the Atlantic Ocean on one side, and Lake Erie on the other, for — unlike any other 
State except New York — its one slope rests upon the tide, and its other upon the Lawrentian 
Lakes. Like all the wide belt of country S.W. of New England, which is centrally traversed by 
the Appalachian Chain, and has the Atlantic Slope on the one border and the slope into the 
Ohio Basin on the other, Pennsylvania possesses three climates ; but from the cause already 
assigned — the proximity of the Ocean and the Lakes — these climates are tempered from the 
more extreme types they exhibit in the other parts of this zone. The Atlantic Slope, including 
the tide-water plain at its base, is much wider throughout the Southern States, and both it and 
the mountain-chain behind it are therefore further removed from the influence of the ocean ; 
and, again, the Western Slope of the State, by its inland position, is so far withdrawn from the 
hot plain encircling the Gulf of Mexico, that the S.W. wind of the continent, a most important 
element in our climates, is materially tempered in both its heat and humidity. To these sources 
of a comparatively equable climate, should be added the relatively lower elevation in Pennsylvania 
of the mountain-chain, the mean height of which increases towards both the N.E. and the S.AV. 

My object here is to present merely a general outline of the climatal features of the State, 
there being no room in this work for local details on this subject. I shall therefore best succeed 



TEMPERATURE. 



53 



by presenting the chief climatal elements of temperature and moisture, in their average and 
extreme amounts. 

Tempemture, — Average of the Year. — The mean or average temperature of the entire State 
is very nearly 47°, or about that of the Island of Great Britain. When we contrast the latitudes 
of the two countries, the mean of the one being scarcely as high as hit. 41°, that of the other 
being lat. 54° 20', this coincidence of mean temperatures is not a little remarkable. It is inter- 
esting as indicating why this portion of the United States seems more congenial than any other 
to the British, German, and other populations emigrating to America from the north temperate 
climates of Europe. 

The Northern Border of the State has a mean temperature, with a certain fluctuation due to 
height, of about 45°, but the north-western corner or western part of this northern Ijelt possesses 
a mean annual heat of about 47°, the difference being evidently due to the ameliorating action 
of the broad surface of Lake Erie. 

The Southern Border, or rather the belt S. of a line stretching from Easton to Pittsburg, has 
a mean temperature of about 50°. So marked a difference in the temperatures of the northern 
and southern sides of the State, equivalent to a change of 1° of Fahrenheit for every 25 or 30 
miles difference of latitude, contrasts strikingly with the more gentle gradations of climate in 
Western Europe and on the Pacific side of North America, where the average rate of variation is 
at the least 60 miles, or 1° of latitude to 1° of temperature. It is plain, therefore, that Penn- 
slyvania, in common with all the country north of it as far as Hudson Bay, contains, for its 
breadth in a N. and S. direction, a remarkably wide range of climates. In other words, it has 
its different climatal zones very closely compressed. 

A given mean annual temperature will not be found to range due E. and W. across the State; 
but the Isothermal Lines, or those marking identical average heat, are deflected southward where 
they cross the mountains. This arises from the circumstance that elevation above the sea, 
especially where the mountains are near it, is a main cause of coolness. So that we must go S. 
along the mountains a certain distance to find the same temperature which we have been tracing 
towards them over the plains. In crossing the Appalachians of Pennsylvania, the mean annual 
heat, under the same latitude, appears to decline about 3°, and therefore the Isothermal Lines 
must swerve to the southward in the highest portions of the chain al)Out 75 or 100 mUes, 
resuming their latitude when they descend into the plain of the Alleghany and Ohio Eiver. 
These are the conditions of the average heat of the whole year ; let us look next at the relations 
of temperature for each of the four seasons. 

Mean Temperature of the Spring Months. — According to the temperature charts and tables, 
published recently by Mr Lorin Blodget, our best authority on the climates of the United States, 
the average temperature for the three spring months of the southern edge of the State is about 
50°, while that of its northern border, excepting the Lake Slope, where it is 45°, is very nearly 
44°. Thus the spring mean temperature of the entire State is about 47°, or the same as that 
of the whole year. The Mountain Zone is cooler by 2° or 3° than the South-eastern and North- 
western Slopes. But elevation appears to exert a less sensible influence in reducing the tempera- 
ture in the spring than during either of the three other quarters of the year. 

Summer Mean Temperature. — The mean temperature of summer of the southern half of the 
State is about 70°, and that of the northern half about 67°; but at this season the Mountain-zone 



54 



CLIMATOLOGY. 



is so mucli cooler than the Atlantic and Western Slopes, that to get a clear notion of the summer 
climates we must divide the State, for this period at least, into its three Belts, — a south-eastern, a 
middle, and a western. Thus the mean summer temperature of the district between the tide-water 
and tha first range of mountains is about 72^" ; that of the Mountain Belt is about G7° ; and that of 
the western side of the State, very nearly 69° ; in other words, the cooling influence of the moun- 
tains, contrasted with the Atlantic Slope, is equivalent to a mean difference of 5g°, or more than 
twice their effect in the spring season. The difference of 3^° between the eastern and the western 
slope or plain, is evidently somewhat more than is due simply to a difference of elevation, and 
must be ascribed in part to the proximity of the Atlantic Slope to the low, warm plain of the 
tidal sea-board of the Southern States. The mountain climate of the State, as might be inferred 
from its average summer temperature of 67\ is eminently tonic and salubrious to constitutions 
debilitated by the greater and more protracted heat of the lower country. 

Autumn Mean Temperature. — The average temperature of the whole State in the autumn 
seems to be about 50°, that of the Atlantic Slope approximately 54°, and that of the Ohio Slope 
about 52°. At this season the cooling influence of height is very sensibly felt in the mountains ; 
it is indicated in the much earlier arrival there of frost and snow than in the south-eastern and 
western plains. 

The Winter Mean Temperature. — Elevation exerts at this season of the year so marked an 
influence in the distribution of temperature, that it is expedient again to consider the climatal 
zones as coinciding nearly with the three great Orographic divisions of the surface — the two 
slopes and the intervening mountain-chain. So viewed, the Atlantic Slope has, for this season, a 
mean temperature of about 30°, the Mountain Belt approximately 24°, and the Western Slope nearly 
28°. It is an important feature in the climate of the southern border of the State that the mean 
winter temperature of 32°, or the point of freezing and melting, lies along a line just coincident with 
the edge of tide-water, touching Trenton, Philadelphia, and the Susquehanna, near Port Deposit. 

Summary. — From the above data, it would appear that the Atlantic slope exhibits a range 
from mean winter to mean summer temperatures of 42|^°, namely, from 30° to 72°.5 ; the 
Mountain Chain a like range of 43°, namely, from 24° to 67° ; and the Western Slope a similar 
one of 41°, namely, from 28° to 69°. 

The corresponding mean annual range for the climate of Great Britain is about 20°. 

Exti^emes of Temperature.— The climate of Pennsylvania exhibits, like every portion of the 
United States east of the Eocky Mountains, very wide extremes of temperature, both periodic, 
or annual and diurnal, and non-periodic, or casual, namely, sudden rises and falls of heat con- 
nected with the shiftings of the weather. These oscillations are, however, less extreme in the 
Middle States than in perhaps any other district of the eastern half of the continent, certainly 
less extreme than in New England and the States west of the Mountains. 

The Mean Maximum Temperature for the summer season, averaging the whole of Pennsyl- 
vania, is about 74°, and the Mean Mmimmn Temperature for the same is about 65°. These are 
important data for indicating the adaptation of the climate for certain crops, for it is the summer of 
the year, more than any other portion of it, which has a critical relationship to agriculture. The 
summer temperatures and the summer moisture control all vegetable life, and even animal life, 
to a large extent ; and upon them depend many of man's most important interests. The extremes 
of summer and winter temperatures are the most important of the limiting conditions of life, 



TEMPERATURE. 



55 



determining what plants and animals can, and what cannot, flourish naturally or through 
artificial culture, and a correct statement of them is fully as essential to the thorough definition 
of any climate as the mention of its annual, seasonal, and monthly mean temperatures. It is to 
be regretted that the casual or non-periodic oscillations of weather have hitherto received from 
meteorologists, in their descriptions of climate, so little attention. Up to the present time there 
is almost no temperature-chart before the public which indicates, in addition to mean isothermal 
temperatures, the known or possible extremes of heat and cold for each district or zone of 
country. In the present incompleteness of the published records of temperature, I find it diffi- 
cult to procure a statement of the extremes of heat and cold to which the interior localities of 
Pennsylvania are liable. Mr Blodget's excellent treatise on the Climatology of the United States 
furnishes ample data concerning the thermal fluctuations at Philadelphia, and I must content 
myself with presenting, in the most condensed shape, a simple statement of these. In place of 
exhibiting the vicissitudes of temperature for every month of the year, I prefer, for the sake of 
brevity, to introduce only those of the five warmest months and the three coldest, since these 
contain nearly all the elements which are useful for the comparison of the extremes of one 
climate with those of another, and all the conditions influential to agriculture, horticulture, and 
the other arts especially affected by climate. 

The following Table exhibits not only the greatest degrees of heat and cold felt in each of 
the eight months referred to, over a term of nearly sixty years ending with 1856, but it also states 
the lowest or coolest maximum temperature experienced, and the highest or warmest minimum 
in each month : — 



j^j^^ f Highest maximum, or greatest heat known, 94° Lowest maximum, or least heat known, . . 71° 

' ( Lowest minimum, or greatest cold known, 32° Highest minimum, or least cold known, . 55° 

-r ( Highest maximum, .... 98° Lowest maximum, 81° 

June, ■■<,-. .. o ^. , . 

(_ Lowest mmimum, .... 42 Highest minimum, 62° 

July -f -^'S'^^^* maximum, .... 98° Lowest maximum, 86° 

' ' 1 Lowest minimum, .... 55° Highest minimum, 65° 

August ^ Highest maximum, , , . . 96° Lowest maximum, 85° 

' ( Lowest minimum, .... 50° Highest minimum, 69° 

September ^ S^ighest maximum, .... 93° Lowest maximum, 78° 

' Lowest minimum, .... 35° Highest minimum, 55° 

Decembee -f -^'S^iost maximum, . . . . 72° Lowest maximum, 44° 

' ( Lowest minimum, . . . . 2° Highest minimum, 25° 

January -f ^^S^est maximum, .... 66° Lowest maximum, 40° 

' (, Lowest minimum, . . . . — 10^ Highest minimum, ..... 24° 

February ^ Highest maximum, .... 70° Lowest maximum, 44° 

' ( Lowest minimum, .... 7° Highest minimum, 17° 



The above record of temperatures, remarkable as it is, fails to show the extreme degrees of 
heat and cold, especially the latter, which belong occasionally to the climate of Philadelphia. It 
is stated by Blodget, on the authority of Pierce, that in 1780, which was the coldest winter known 
until the two last, 1856 and 1857, " the Delaware Eiver was closed from the 1st December to the 
1 4th March, and that during the month of January the mercury was several times between 1 0° 
and 15° below zero, and only once during the month as high as 32'." The winter of 1783-1784 
seems to have been almost as intensely cold. 

Philadelphia, seated on the tide-water, does not offer, however, a fair specimen of the climate, 



56 CLIMATOLOGY. 

or rathier climates, of Pennsylvania. Its winter extremes of cold are less by many degrees than 
those experienced in higher and more interior localities ; while its extremes of heat are only a little 
if at all greater. Thus at Lamhertsville, on the Delaware, a station which represents very fairly 
the climate of the Atlantic Slope of New Jersey and Pennsylvania, the highest maximum tem- 
perature during nineteen years, ending with 1855, is recorded at 100°; Avhile the lowest minimum 
is given at — 16°.5. This exhibits a range of 116°.5 ; or 5° or 6° greater than the range at 
Philadelphia. The ordinary or memi annual range for this city is 85°. This is the difference 
between the average of the extreme coldest temperatures of all the winters for sixty years, and 
the average of the extreme warmest for the same term. As an illustration of the difference 
between Philadelphia and the interior in their degrees of extreme winter cold, the winter of 
1835, an uncommonly severe one, showed a cold of —22° at Lancaster, and of —24° at Pottsville ; 
while at Philadelphia it was only —6°. Again, in 185G, while the lowest temperature at Phila- 
delphia was — 7°, that at Pittsburg was — 1 8°. 

Rain Averages for the Year.- — Few districts of the United States, or indeed of the world at 
large, are more fortunately circumstanced as to rain than Pennsylvania. Lying within the 
belt of the non-periodic rains, it is blessed with a singularly equable distribution of moisture 
throughout the year. The State is seldom visited by a drought of more than six weeks' duration, 
generally occurring, when it does take place, in the latter half of the summer. These dry 
periods, hardly more frequent than once in four or five years, are rarely so severe as those which 
visit the west and some other parts of the country. It is, in like manner, comparatively exempt 
from protracted and flooding rains. The rains of Pennsylvania, New Jersey, and Eastern New 
York take the form of brief, light, rain-storms of one, two, or at most three days' duration, and 
of intermitting showers ; and these, excepting during the occasional summer and autumn 
droughts, are spread with remarkable impartiality over the several seasons, and even over all 
the several months of the year. 

At Philadelphia and along the Atlantic Slope of the State, the average annual rain-faU 
amounts to 42 or 43 inches. In the Appalachian Chain and on the Ohio Slope, it is materially 
less. Thus, at Carlisle, the average for six years has proved to be only 34 inches ; and at 
Pittsburg, the average for eighteen years is a little short of 35 inches. This diflerence in the 
atmospheric precipitation on the Atlantic Slope and in the mountains, is a ciuious exception to 
the general law of rain in many countries, where the mountains receive much more than the 
j)lains, even though the plains lie close to the sea. It would seem to imply, that the mountain 
rains of Pennsylvania are derived in considerable amount from the far-removed Gulf of Mexico, 
the S.W. wind from which has parted with a large share of its moisture on its journey, 
while the Atlantic Slope, or sea-board, receives an additional supply from the more local winds 
of the ocean. 

At Philadelphia, the fall of rain for each of the four seasons averaged, during nineteen years 
ending with 1856, — for spring, 10.97 inches; summer, 12.45 ; autumn, 10.07 ; winter, 10.06. 

At Pittsburg the respective amounts, during eighteen years ending with 1854, were, — spring, 
9.38 inches ; summer, 9.87 ; autumn, 8.23 ; winter, 7.48. 

Extreme Quantities of Rain. — The total annual supply of rain fluctuates considerably in all 
parts of Pennsylvania, in accordance with the general non-periodic character of all the elements 
of its climate. Thus at Philadelphia, during twelve years, the fall in shape of rain and snow was 



EAIN AND WINDS. 



57 



one year only 35 inches, while another it was nearly 55 inches. At Pittsburg, during eighteen 
years, one year had 25.6 inches, while another year had 47.8 inches ; and Gettysburg, near the 
mountains, had, in different years, 30.2 inches, and 52.2, in a term of seventeen years. Still 
more remarkable are the yearly variations in the rain-fall at New York. In a term of nineteen 
years, ending in 1854, one year (1837) produced 65.5 inches, while 1840 gave rather less than 
30 inches. It is stated by Mr Blodget, that in the Central States of the Union, about two and a 
half times the least observed quantity of water falls during certain years, — that in some years 
less than half the average descends, and in others nearly double the average quantity. 

At Lambertsville, the greatest number of rainy days for eighteen years has been 118 ; the 
least number 85. 

At Fort Mifflin, on the Delaware, below Philadelphia, the greatest number of rainy days 
recorded is 110, and the least number 86 ; while the greatest number of snowy days is 17, and 
the least number 11. 

At Carlisle, the highest number of rainy days recorded is 93, the lowest number 68 ; and the 
highest number of snowy days 26, the lowest number being 19. 

At Pittsburg, the greatest number of rainy days for any one year has been 153, the least 
number 101 ; while the greatest number of snowy days has been 35, and the least number 13. 
The average number of the latter being 25. 

Comparing the conditions of rain near the Tide-water with those at Pittsburg, we find that, 
while the former enjoys 7 inches, or 20 per cent more actual rain and snow than the latter, the 
relation is reversed as to the number of rainy and snowy days, the western locality exceeding the 
eastern in nearly as great a ratio. 

Prevailing Winds. — The dominant winds in Pennsylvania, as in so many other parts of the 
United States, are the westerly ones ; but its several regions differ materially in the proportionate 
amount of the winds from the various quarters of the compass. Adhering to our division of the 
State into its South-eastern, Middle, and Western Climatal Zones, we have the elements for 
comparing the winds of each in the excellent summaries of observations on wind and weather, 
contained in the Meteorological Tables of the Medical Statistical Eeport on the Army of the 
United States, prepared under the direction of the Surgeon-General. Collecting the data there 
recorded for the localities of Alleghany Arsenal at Pittsburg, Carlisle Barracks at Carlisle, and 
Fort Mifflin on the Delaware, during the twelve years from 1843 to 1854 inclusive, I find that 
the winds were as follows ; — the circle of the horizon being divided into eight equal segments of 
45° each, the number of days within the year on which the wind blew from each of these direc- 
tions was — ■ 

N. N.E. E. S.E. S. S.W. W. N.W. 

-Pori! J///J?m (average of only six years), . . . 24 50 25 30 32 75 51 65 
CaWis^e ^a?v«cX-s (average of seven years), . . 16 17 73 26 24 18 126 53 
Alleghany Arsenal, Pittsburg {iiYexdLg& oit^dYey^diXii), 49 42 26.5 16 27 59 55.5 46 

It will be seen from the Table, that on the sea-board the most frequent wind of all is the 
S.W. This is likewise somewhat the most abundant wind at Pittsburg, but at Carlisle Barracks 
the W. wind greatly predominates over all the others ; though a part of the 126 days recorded 
as west wind is evidently the S.W. current undergoing a local deflection from the dying away 
of the lofty chain of the Blue Kidge, near this place, and the sudden opening thereby of the low 
Atlantic Plain to this somewhat pent-up breeze. All the three divisions of the State display 

VOL. I. H 



58 



CLIMATOLOGY. 



a marked superiority of the winds of tlie nortli-Avesterly over tlie soutli-easterly half of the compass- 
circle. At Fort Mifflin, the three v^^esterly winds — namely, S.W.,AV.,and N.W.,blow 191 days; while 
all the other five blow for only 1 G 1 days. At Carlisle Barracks, the predominant winds are the 
W., N.AY., and E., occupying together 252 days ; but it is evident that this locality, the only one 
within the Mountain Chain whose winds have been reported on, is not happily situated for the 
purpose. Its N.E. winds amount to but 17 days, while its E. winds blow for 73 days. These 
latter are plainly, in part, the N.E. currents, deflected by the topography of the country. At 
Pittsburg, all the five winds, S.W., W., N.W., N., and N.E., are of nearly equal frequency, the 
S.W. and the W. somewhat preponderating. The three other winds, the E., S.E., and S., are 
comparatively infrequent, and in this feature the region resembles closely the tide-water front of 
the State. 

Situated just far enough to the south to escape the severity of the cold and humid N.E. 
Avind of the New England coast, and the savage energy of the intensely cold parching N.W. 
blasts of the northern interior of the continent, and just far enough N. to avoid the full heat 
and sultriness of the humid and relaxing S.W. and S.E. winds from the Gulf of Mexico and 
the warm Atlantic, this happily placed region is endowed with a climate possessing fewer of the 
noxious qualities of the general climate of the eastern half of the continent, than any other 
equal territory seated between the Atlantic and the Eocky Mountains. 



GEOLOGY. 



GENERAL INTRODUCTORY CHAPTER. 

CLASSES OF EOCKS EMBEACED IN PENNSYLVANIA. 

An inspection of any good geological map of the United States, and the British Provinces, will 
show that Pennsylvania embraces only the more ancient systems of strata of this portion of the 
continent. It includes no deposits of the Tertiary or Kainozoic age ; none belonging to the 
Cretaceous or Greensand, nor any referable to the somewhat older Oolitic period. 

Tertiary and cretaceous strata border the State upon the S.E., in New Jersey, but they do 
not cross the Delaware River into Pennsylvania. 

The strata upon which the surface- wash and soils of Pennsylvania repose, belong to the three 
oldest classes of the sedimentary rocks — namely, to the Gneissic, the Paleozoic, and the earliest 
Mesozoic ; each, but especially the Paleozoic, being developed upon a scale of great magnitude. 

No large masses of igneous or volcanic rocks of any description appear within the borders of 
the State, the only intrusive materials being a few bold dykes of trap-rock, and innumerable 
lesser veins of the granitic rocks, all confined to the south-eastern district. 

Of the three groups of strata above mentioned, the gneissic, or ancient metamorphic rocks, 
and the mesozoic red sandstone formation, occupy about an equal extent of territory, and are 
limited to the south-eastern counties. The paleeozoic rocks cover about nine-tenths of the surface 
of the State ; they possess an enormous aggregate thickness ; divide themselves into many series, 
which again subdivide into numerous formations ; they include a great profusion of organic 
remains, and exhibit in their undulations every diversity of structural feature to be met with in 
the Appalachian Chain, and they enclose an extraordinary amount and variety of the mineral 
deposits most useful to the wants and purposes of civilised man, particularly coal, and the chief 
ores of iron. 

A large proportion, therefore, of this work will be devoted to a description of these Appala- 
chian Palaeozoic formations. 

Resting upon these three great groups of solidified or rocky strata are sundry loose super- 
ficial deposits, some of which are invested with sufiicient interest to demand a general descrip- 
tion. These are chiefly certain soils, the ferruginous loams of the hematitic iron ores, and the 
northern Drift or Diluvium. 



60 



ROCKS OF PENNSYLVANIA. 



The Gneissic or H}'pozoic rocks of the State inchide nearly all the more common varieties of 
felspathic, horublendic, and micaceous gneiss and mica-slate. Closely associated with these, yet 
belonging to a wholly different system of strata, are extensive formations of talcose and micace- 
ous slates, indurated clay-slates, chloritic and steatitic slates, referable in strictness to the palaeo- 
zoic system, but so thoroughly metamorphosed through diffused igneous action, as not to be 
easily separated in detail from the true gneissic class. To this group of the crystalline strati- 
fied rocks have generally been referred the altered Primal slates, and Primal white sandstone, and 
also the crystalline limestone, or white and bluish marble of Montgomery, Chester, and Lancaster 
counties ; but I shall show that these great strata do not truly date with the proper gneissic 
group, or so-called primary rocks, but are of palteozoic age, and identical, in fact, with the widely- 
spread primal and auroral rocks of the fossiliferous or secondary period. 

The PalcEOzoic Rochs, the full classification and detailed description of which will be intro- 
duced in a subsequent chapter, constitute a vast succession of fossiliferous strata, commencing 
(in ascending order) with the lowest fossiliferous deposits resting on the gneissic class, and termin- 
ating with the last or highest of the coal strata. A comparison between their numerous organic 
remains and those of the palaeozoic strata of Europe has satisfactorily shown that these rocks were 
deposited, with certain interruptions, during all the four earliest periods of the five great Euro- 
pean divisions of palaeozoic time, namely, the Cambrian, Silurian, Devonian, and Carboniferous 
ages. Neither in Pennsylvania, nor in any other quarter of North America yet explored, have 
rocks of the fifth or latest palaeozoic period, called the Permian, been discovered. 

The prolonged succession of sedimentary actions, producing these enormous strata of the 
Appalachian system, ceased with the close of the Carboniferous era, the whole formative process 
being terminated by the upheaval of the ocean, in whose broad bed and around whose margin 
the deposits had been collected. In the region of the palaeozoic basin of Europe there was a 
similar upheaval at the end of the Coal period ; but it was more partial, leaving a reduced but 
still wide area of waters for the reception of the next subsequent group, the Permian, Though 
the Appalachian palaeozoic strata represent, therefore, a somewhat less extended scale of geological 
time than the European, they compensate for this deficiency in their extraordinary thickness, in 
the abundance and variety of their organic remains, and in the number of the separate, well- 
defined fossihferous horizons, or independent platforms of extinct life which these display. 

As developed in Pennsylvania, the aggregate thickness of these ancient deposits is not less, 
according to measurements carefully executed, than about 3.5,000 feet, and the scale upon which 
some of the constituent formations were produced was proportionately grand. Some of these 
formations, well defined by their organic remains and their lithological composition, measure 
individually between 3000 and 5000 feet. The strata of the Appalachian system of Penn- 
sylvania (and the description aj)plies equally to those of other regions) exhibit a remarkable 
variety of mineral character. They may, however, be aU embraced under the thi-ee prevailing 
generic classes of the sedimentary rocks, namely, Sandstones, Slates, and Limestones ; enclosing 
as subordinate layers, lesser deposits of coal, chert, and iron ore. 

The coarser mechanically-produced strata consist in a large degree of silicious fragments, 
partly forming thick and massive Conglomerates of quartz pebbles, partly grey and whitish 
quartzose Sandstones. Other formations of great thickness, and wide, horizontal expansion, have 
an argillaceous composition, and are of the class called Argillaceous Sandstones and Sandy Shales. 



EOCKS OF PENNSYLVANIA. 



61 



Many of these solidified sandy clays are brown and reddish ; others, of less thickness, are grey, 
greenish, and even yellow. The more purely argillaceous rocks of the system are certain enor- 
mous formations of clay-slates and shales, of very various aspects and textures. Some of these 
are grey and bluish ; others are red ; while certain others, again, consist of clay and sand stained 
by the red oxide of iron. Besides these, there is another important class deficient in the silicious 
ingredient, and abounding in clay and the carbonate of lime, in those proportions which consti- 
tute maids or calcareous shales. These are frequently variegated, showing many tints in com- 
paratively thin alternating strata. 

Not the least interesting and important class of the Appalachian rocks are the true Limestones. 
They consist for the most part of an union of carbonate of lime and carbonate of magnesia, though 
some of them contain only a small amount of the latter ingredient ; others, again, include 
much argillaceous matter, and some are very sandy, and should be called Shaly and Silicious 
Limestones. 

All of these deposits are more or less fossiliferous. Their distinctive peculiarities of composi- 
tion, their characteristic organic remains, and their constituents generally, will be dwelt upon 
in the .subsequent parts of this work. 



PART 1. 

METAMOEPHIC STEATA OF PENNSYLVANIA. 

♦ 

INTRODUCTORY CHAPTER. 

CLASSIFICATION OF THE METAMORPHIC STRATA OF THE ATLANTIC SLOPE OF 
THE MIDDLE AND SOUTHERN STATES. 

Before entering upon a special description of the older rock-formations of Pennsylvania, with 
which our detailed account of its geology must commence, it will be expedient, for a clearer 
understanding of their relations to each other, to present a concise sketch of the geological 
composition of the Atlantic Slope of the Middle and Southern States, of which the Formations in 
Pennsylvania are a portion. 

Discarding from our present survey the newer deposits of the region, or those long, narrow, 
superficial troughs of unconformahly overlying red and grey shales and sandstones of Mesozoic 
or middle-secondary age, wliicli partially cover the older or crystaUine and semi-crystalline strata, 
and restricting our attention to these, we shall find that, when carefully studied, they rank them- 
selves — so far as they admit of subdivision at all — into three natural physical groups. All the 
sedimentary mineral masses, without exception, are in a condition of more or less metamorphism 
or transformation from the earthy to the crystalline state by heat, and therefore, in using the 
term in a critical sense, all of them are metamorphic rocks. In the more current conventional 
application of this word, however, only some of them pertain to the usually recognised meta- 
morphic or gueissic series ; others belong unequivocally to the Palaeozoic or ancient life- 
representing system ; while others, again, constitute an extensive intermediate group, not 
typically gueissic or granitoid in their degree of crystalline structure or metamorphism on 
the one hand, nor yet fossiliferous on the other, so far as the closest scrutiny reveals. For a 
long; while — indeed, from the commencement of geoloofical research in this district of the Atlantic 
Slope until the geological surveys of Pennsylvania and Virginia had disclosed the composition 
and structure of the region — all of these ancient and more or less altered strata, between the 
summit of the Atlantic Slope in the Blue Ridge and South Mountain and its base at the margin 
of Tide-water, were regarded and designated alike as Primary Rocks, and were supposed to 
constitute but one group, the oldest kno^\^l to geologists. Early, however, in the course of 
those surveys, it came to light that by far the larger portion of the rocky masses of at least the 



METAMOKPHIC STRATA. 



63 



middle and north-western tracts, including much of the Blue Eidge and of the Green Mountains, 
were of a different type and age from the oldest metamorphic or true gneissic system. The 
evidence in support of this conclusion was, first, an obvious and very general difference in the 
composition of the two sets of strata ; secondly, a marked difference in their conditions of 
metamorphism ; and thirdly, and more especially, a striking contrast in the direction and 
manner of their uplift, the plications and undulations of the less metamorphic series dipping almost 
invariably south-eastward, while the gneiss in many localities has no symmetrical foldings, but only 
a broad outcrop dipping to a different quarter. These structural dissimilitudes imply essential 
differences in the direction and date of the crust-movements which lifted and transformed the 
respective groups, and they led the geologists of Pennsylvania and Virginia to a conviction that, 
over at least many tracts, there would yet be discovered a physical unconformity both in strike 
and dip. It was not, however, till a relatively late date in the prosecution of the geological 
survey of Pennsylvania, that the geologist of that State detected positive evidences of this 
physical break and of a lapse of time between the two groups of strata, and established, by ocular 
proof, the correctness of the previous induction. This unconformity, reflecting so much light on 
the whole geology of the Atlantic Slope, was first clearly discerned in tracing the common 
boundary of the two formations from the Schuylkill to the Brandywiiie and the Susquehanna, 
but it was quickly afterwards recognised on the borders of the gneissic district N. of the Chester 
County Limestone Valley, and again soon afterwards in the Lehigh Hills at their intersection by 
the Delaware Eiver. 

Prior to the suspension of the geological survey from 1843 to 1851, the true Palaeozoic age 
of the non-fossiliferous crystalline marbles, and semi-crystalline talcoid slates, and, vitreous sand- 
stones of the Chester and Montgomery Valley, had been clearly demonstrated by the State 
geologist through a comparison of the strata with their corresponding formations in a less 
altered condition further north ; but it was not until the resumption of field research, upon the 
revival of the survey in 1851, that any distinctive fossils were detected in these greatly changed 
rocks, which, even in their original state, seem to have been almost destitute of the usual organic 
remains. 

Assembling all the evidence which we now possess, we have in the Atlantic Slope, by actual 
demonstration, but one physical break or horizon of unconformity throughout the whole immense 
succession of altered crystalline sedimentary strata, and within this region but one Palseontologica] 
horizon — that, namely, of the already discovered dawn of life among the American strata. This 
latter plane or limit, marking the transition from the non-fossiliferous or azoic deposits to those 
containing organic remains, lies within the middle of the primal series or group of the Pennsyl- 
vania survey, that is to say, in the primal white sandstone, which, even where very vitreous, and 
abounding in crystalline mineral segregations, contains its distinctive fossil, the Scolithus linearis. 
The Primal slates beneath the sandstone, and in intimate alternation with it, possess not a vestige 
of organic life, nor has any such been yet discovered anywhere within the limits of the Atlantic 
Slope, or on the northern or western borders of the Great Appalachian Basin of North America, 
either in this lower primal slate or in the other semi-metamorphic grits and schists physically 
conformable with it, and into which the true Palaeozoic sequence of our formations physically 
extends downwards. We have thus, then, two main horizons suljdividing the more or less 
metamorphic strata of the Atlantic Slope into three systems or groups : the one, a physical 



U METAMORPHIC STRATA. 

break or interruption in the original deposition of the masses ; the other, a life-limit or plane 
denoting the first advent, so far as yet discovered, of organic beings. As these two planes are 
not coincident, but include between them a thick group of sedimentary rocks, separated from 
the lower physically, from the upper ontologically, we are fully authorised, in the existing state 
of research, to employ a classification which recognises a threefold division of all these lower 
strata. To the most ancient or lowest group, it is proposed in this work to continue the name of 
Gneiss, preferring, however, to call this division generically the Gneissic Series, employing some- 
times the technical synonyme Hypozoic, proposed by Professor John Phillips for the lowest of 
the metamorphic strata. To the great middle group, less crystalline than the gneissic, and yet 
destitute of fossils, the descriptive terms Semi-metamorphic or Azoic are applicable. And to the 
third uppermost system, or entire succession of the American Appalachian strata, from the Primal 
containing the earliest traces of life to the latest true Coal rocks or last deposits of the Appalachian 
Sea, it is here proposed to affix, as for many years past, the weU-chosen title conferred on corre- 
sponding formations in Europe, of the Palaeozoic, or ancient life-entombing system or series. Thus 
we have the Hypozoic rocks, or those U7iderneath any life-bearing strata ; Azoic, or those destitute 
of any discovered relics of life ; and PalcBOzoic, or those entombing the remains of the earth's 
most ancient extinct forms of once living beings. 

The Atlantic Slope of Pennsylvania includes all these three systems of strata, but our first 
concern is with the lowest, or most ancient, the Hypozoic or Gneissic Eocks. It will be seen 
further on in our description of these, and of the Azoic strata, where the latter display their 
maximum amount of crystalline structure or metamorphism, that the members of the two groups 
often simulate each other so closely, and are indeed so identical in mineral aspect and structure, 
as to baffle all attempts at distinguishing them lithologically ; nevertheless, it will clearly appear 
from the evidence embodied in the sections illustrating this country, that they are distinct 
systems occupying separate zones, susceptible of delineation on the geological map. 

At the time of the first construction of the general Geological Map of the State, the true 
limits separating the Hypozoic or Gneissic from the Azoic or Semi-metamorphic rocks were 
but vaguely understood, and the' State geologist did not venture to define them on the map, but 
shaded the one system into the other ; indicating, however, what he has since proved, that the 
true gneissic rocks, in their south-westward course, pass out of the State at its southern 
boundary, a short distance E. of the Susquehanna, while the Azoic or talco-micaceous group, as 
a genuine downward extension of the Primal palaeozoic series, widens progressively, going 
westward, until, from a very narrow outcrop at the river Schuylkill, it occupies at the Susque- 
hanna the whole broad zone S. of the limestone valleys of the Conestoga and Codorus streams in 
Lancaster and York counties. Since the revival of the field-work of the survey, the dividing 
limit of these two sets of metamorphic strata has been traced and mapped with precision. To 
the S.W. of the Susquehanna, it has never, it is believed, been pursued through Maryland and 
the other Southern States, though one may readily discern it in going northward or westward 
from Baltimore, or ascending the Atlantic Slope in Virginia. In Maryland, it crosses the Balti- 
more and Susquehanna railroad about 12 miles N. of Baltimore, and it is intersected by the 
Baltimore and Ohio raiboad a little E. of Sykesville ; it crosses the Potomac about 40 miles above 
Georgetown and the James Eiver in Virginia, 40 or 50 miles W, of Kichmond. The line of 



METAMOEPHIC STRATA. 



65 



boundary is, however, not a simple one, but is intricately looped, in consequence of numerous 
nearly parallel anticlinal foldings of the strata, sending promontories or fingers of the older 
rocks within the area of the newer or semi-metamorphic, to the W. of their average boundary, 
and causing, of course, corresponding troughs, or synclinal folds of the newer, to enter, eastward 
of the average boundary, the general area of the older. The Atlantic Slope has received hitherto 
so little exact geological study, that we are as yet without the data for determining, with any 
precision, either the succession of its much-broken and closely-plicated strata, or the geographical 
limits which separate even the larger sub-groups. It is sufficient, however, for our present 
purpose, to show the existence, and the approximate range, of two great metamorphic systems, 
separated by a physical break, and the conformable relations of the later, or upper of these, to 
well-known lower Palseozoic formations of the Appalachian Chain. 



VOL. I. 



I 



GNEISSIC 



BOOK 

ROCKS OF 



I. 



PENNSYLVANIA. 



4 

GENEEAL DISTEIBUTION OF THE GNEISSIC OK ANCIENT METAMOEPHIC STEATA. 

Tlie three Gtieissic Districts. — Within the limits of tlie State there are three distinct tracts, 
or zones, of the Older Crystalline Gneissic Strata.- 

T/ie First of these, which I shall call the Southern District, ranges from the Delaware at Trenton 
to the Susquehanna, south of the State line, and lies wholly S. of the Limestone Valley of j\Iont- 
gomery and Chester counties, except near its eastern end, where a spur of the gneiss encompasses 
it on the N., and extends thence eastward to Trenton, along tlie margin of the Mesozoic Red Shale. 
This, the largest of the gneissic tracts, breaks oft" to the AV. of the Braudywine, in a succession 
of narrow tongues. Near the State line of Delaware it sends forward, however, through the S.E. 
corner of Chester County and the State of Maryland, a continuous and widening belt to the 
Susquehanna. It is widest in the meridian of Chester and Eidley creeks, where it spreads from 
near old Chester to within a mile and a half of the Paoli. 

The Second Zone lies N. of the North Valley Hill, extends lengthwise from near A^'alley Forge 
to the West Branch of Octorara Creek in Lancaster County, and expands northward from the 
foot of the North Valley Hill to the southern edge of the Red Sandstone district, or Valley of 
French Creek and south base of the Welsh Mountain, in Chester County. 

The Third Zone or District of the Gneissic Rocks is confined to the belt of hills ranging from 
the Delaware below Easton to Reading on the Schuylkill, known as the South IMountains. This 
tract, prolonged from the Highlands of New Jersey, follows this range of hills to where they 
subside near the Schuylkill, the gneiss being flanked on the S.E. by the upper margin of the 
Mesozoic Red Sandstone, and on the N.W. by the Primal White Sandstone, and Auroral Limestone 
of the lower border of the Great Appalachian Valley. Within these general limits, the Gneissic 
rocks occupy, for the most part, the higher ridges and their slopes, while the Palaeozoic strata 
repose in the included valleys, and at the northern base of the Chain. 



CHAPTEH I. 



SOUTHEKN ZONE OF GNEISS, 

OR GNEISSIC EOCKS SOUTH OP THE MONTGOMERY AND CHESTER VALLEY. 

Observing the prescribed order of description, we shall begin our account of these ancient 
metamorphic strata with the Southern district, or that south of the first limestone- valley. But 
in order to exhibit fully at the outset its structure and composition, it will be expedient to depart 
from our usual rule of tracing each tract from E. to W., and begin in the middle, where the belt 
is broadest and most fully developed. Here we have the benefit of the fine natural section and 
series of artificial exposures furnished by the River Schuylkill. 

Boundaries.- — -This most southern belt of our crystalline strata makes its first appearance at 
a spot in New Jersey, about six miles N.E. of Trenton, where it emerges from beneath the margin 
of the overlapping Mesozoic Red Sandstone. From thence it gradually expands in its course 
south-westward, keeping the southern border of Pennsylvania to Delaware and Maryland. 

Its lower or south-eastern margin crosses the Delaware River a short distance below the bridge 
at Trenton, and passes by Bristol, Philadelphia, Chester, and Wilmington, being separated from 
the river by a narrow strip of Diluvial and Alluvial deposits, which only in a few places exceed 
one mile in width. The northern boundary, commencing at the same point in New Jersey, 
crosses the Delaware about a mile and a half above Trenton, and ranges in a somewhat undulat- 
ing line to Sandy Creek, about a mile E. of the Wissahickon. 

W. of the Wissahickon, the northern edge of this zone of the gneiss ranges just S. of Barren 
Hill ; crosses the Schuylkill a little below Spring Mill, passes about a mile and a half S. of the Paoli, 
and terminates near Boardsley's Run of the West Branch of the Brandywine, and not far 
from the Chester County Poor-House. W. of the Brandywine, the gneissic rocks sink under 
the altered Primal strata, in a succession of anticlinal fingers, on slender promontories, the boun- 
daries of which will be given when we come to trace their distribution in detail. 

DETAILS OF THE SOUTHERN GNEISSIC DISTRICT. 

Gneissic Rocks of the Valley of the Schuylkill, hetiveen Philadelphia and Spring Mill* — 
Commencing at Fairmount on the Schuylkill, and following the E. Bank of the river in a 
general north-westerly direction, our geological section intersects the strata nearly at right angles 
to their strike. It presents the formation under a great variety of features and of composition ; 
the several kinds of gneiss alternating in considerable frequency with each other. It is not 
possible to divide the whole of this broad belt of Gneissic country, and the Palaeozoic belt of 
Montgomery and Chester, into any very sharply-defined subordinate ranges, for the many difier- 
ently constituted bands of the crystalline rocks either so fade into each other, or are of such limited 

* The reader should here consult the Geological Map and the Illustrative Sections of the Schuylkill and neighbouring valleys. 



68 



SOUTHERN ZONE OF GNEISS. 



length, that to trace and map them in detail would be a work of herculean labour. The strata 
are too generally obscured by a deep covering of loose earth, largely derived from their disinte- 
gration, and the rocks themselves are too deeply rotted and softened by surface action, to permit 
that abundance of salient exposures which would be essential to the recognising and picturing, 
with minute exactness, of their innumerable local bands. Nevertheless, the whole of the gneissic 
system of the Schuylkill may be approximately and conveniently subdivided into the three large 
groups of strata, occupying, where they are intersected by the river, three broad Belts. 

The first, or most southern general Division or group, may be approximately defined as extend- 
ing from the lowest exposures on the river, or those near Gray's Ferry, to the upper end of 
Manayunk ; the second, or middle Belt, extending from Manayunk past the Serpentine and Soap- 
stone range to a line a little N. of the upper boundary of the County or City of Philadelphia ; 
and the third, or northern, extending thence to the northern edge of the whole Gneiss formation, 
as it is overlaid and limited by the older Primal rocks in the vicinity of Spring Mill. 

FiEST Belt. — The southern or Philadelphian Belt contains the following chief descriptions of 
ordinary gneissic rock, with many sub-varieties. The most common or typical variety of all is 
a grey, bluish, rather finely-laminated triple mixture of quartz, felspar, and mica ; the quartz, for 
the most part, white or transparent ; the felspar usually white, and very generally somewhat 
chalky from incipient decomposition ; and the mica, most commonly black or dark brown, and 
in small plates. This rock occasionally includes small insulated garnets. 

The next most common species is a dark, bluish-grey, sometimes greenish-black gneiss, com- 
posed of hornblende and quartz, with sometimes a little felspar, the hornblende always greatly 
predominating. This rock is very usually fine-grained and thinly bedded, its fracture and struc- 
ture being controlled by the general parallel crystallisation of the prevailing hornblende. 

A third common variety of the gneiss of this group is a micaceous quartzose rock, generally 
of a light grey colour. Some beds of this species contain such a predominance of the crystalline 
quartz, in minute granular division, and such a subordinate amount of minutely disseminated 
mica, as to have a character of ordinary grey whetstone ; but this species of the gneiss is much 
more abundant in the middle belt than in the southern one. A much coarser kind of grey 
micaceous gneiss, consisting of a predominance of rather large flakes of mica, with a subordinate 
quantity of felspar and quartz, occurs interstratified with all these other species, as a very usual 
transition variety between the standard grey gneiss and the highly micaceous kinds verging 
towards mica-slate. 

It is very usual to find the typical gneiss, of a threefold constitution, alternating with the 
hornblendic species, and both of these alternating with the quartzose micaceous variety. As a 
general fact, not without exceptions, however, the more micaceous the rock is, the greater is its 
abundance in insulated crystals of common garnet. 

Interposed among the above varieties of true gneiss are beds, more or less thick, of kinds so 
abounding in mica as to be entitled to the designation of true mica-slate. This rock prevails in 
two or three outcrops, both above and below Columbia Bridge, and it may be stated generally, 
that the further north we advance across the southern division of the gneiss, the larger is the pro- 
portion of the more micaceous varieties of the ordinary gneiss, and the greater the frequency of 
these bands of mica-slate. 
. An interesting variety of the ordinary or more felspathic kind, is one containing large, more 



FIRST BELT OF GNEISS. 



69 



or less insulated, segregations of crystalline felspar, tlie longer axes of whose crystals lie generally 
parallel with the lamination of the rock. This variety may be designated a porphyritic gneiss, 
having that feature of an excess of crystalline felspar which is accepted by geologists as a dis- 
tinctive character of the porphyritic rocks, and being, moreover, essentially similar to those well- 
known and beautiful granites which geologists agree to call Porphyritic. 

A band of this porphyritic gneiss occurs at the Falls of Schuylkill, just below the Quarries, 
and ranges towards Nice-Town in one direction, and towards the Toll-gate, on the Lancaster 
Road, five miles W. of Philadelphia, in the other. Another outcrop of the same felspathic 
variety of the gneiss may be seen crossing the West Chester Plank-Road, just E. of Darby Creek. 

The Gneiss rocks, especially the more felspathic varieties, exhibit throughout this southern 
belt an extensive disintegration, pervading them in some localities to a dejJth of many feet below 
the soil. When in this condition, the felspar is either wholly or partially converted into kaolin 
(or China earth), and softened ; the mica is itself also sometimes decomposed, staining the mass, 
from the oxide of iron set free. Such is likewise the case with the hornblende, where this is an 
ingredient. To this susceptibility of decomposition under long-continued atmospheric agency, we 
must ascribe the great prevalence of mica in the soil of this region, and the general absence of 
superficial fragments and boulders of the gneiss, these having, in part at least, wasted into 
soil. By the slow but increasing disintegration of the felspar, a certain small portion of potash 
is constantly furnished to the soil to sustain its natural fertility, and the mica loosened from the 
rock becomes also a valuable ingredient, by giving it a peculiar spongy texture, admirably suit- 
ing it for the retention of moisture. A practical application of this rotted gneiss is occasionally 
made near Philadelphia, the loose materials of the rock being sifted, to procure a sand which is 
of remarkable sharpness, and well suited for the purposes of masonry. 

Granite Veins. — In this soutliern zone of the gneiss formation occur numerous injections of 
true granite. These are for the most part narrow, obscure dykes, or more truly intrusive veins, 
penetrating and branching into the gneiss rocks, which are very generally contorted in their 
vicinity. Frequently these veins expire within the gneiss, only the larger ones having been 
injected with force enough to cut entirely through it. These granite dykes possess a remarkable 
general uniformity of composition and mineral character. The constituent minerals are felspar, 
quartz, and mica, all coarsely, independently, and confusedly crystallised. The predominant 
mineral is white felspar, and the next most abundant constituent is the quartz ; the mica, indeed, 
being frequently almost wanting. The prevalence of felspar imparts to these veins a predominant 
whiteness, which usually enables them to be immediately recognised. It is likewise the cause 
of their generally very rotten condition, for throughout all this district the felspar and other 
easily decomposible minerals are, from some cause, universally and deeply decayed. 

Unstratified or true Igneous Hocks. — Several rocks of the igneous class present themselves in 
the district before us. Of these, one of the most frequently seen is a peculiar felspathic syenite in 
thick dykes, also a white coarse-grained granite composed of felspar and quartz, in tortuous and 
sometimes ramifying veins, and greenstone and other forms of trap-rock in dykes, and also quartz, 
chromiferous iron ore and other minerals, occurring singly or associated in the shape of elongated 
thin dykes or narrow veins. To these should, perhaps, be added some of the masses of serpentine, 
for the unstratified character of these last named is no longer doubtful. 

Syenite. — Of the above-mentioned intrusive rocks, the most largely developed is the species 



70 



SOUTHERN ZONE OF GNEISS. 



■which I have called a Felspathic Syenite. This is for the most part a confused crystalline mixture 
of translucent smoky felspar and quartz, with sometimes a little mica, and more rarely a small 
proportion of hornblende. The felspar frequently forms almost the entire mass of the rock, and 
is always the predominant ingredient. Where it occurs alone, the crystallisation is usually very 
coarse and perfect. In the central portions of the dykes or beds, this rock presents few or no 
traces of any parallelism in its internal structure, much less any genuine stratification, but upon 
the sides where it approaches contact with the strata of gneiss enclosing it, an imperfect strati- 
fication is discernible. This feature is only such, however, as belongs to many dykes of genuine 
igneous granite, and by no means indicates it to appertain to the stratified metamorphic class. 
The rock before us is well adapted to certain purposes of architecture, being much more cohesive 
than the ordinary gneiss rock of the region, and less liable to disintegration under atmospheric 
action. Its chief localities are in the south part of Delaware County, from whence it passes south- 
westward into the State of Delaware, the dykes augmenting in frequency and size as we trace 
them in that direction. This rock has been extensively employed in the construction of the 
Delaware breakw^ater. The largest quarries of it are on Naaman's, Brandywine, and Christiana 
creeks, in the State of Delaware. The localities of the more important trappean and other dykes 
will be mentioned in another place. 

Trap Dykes. — -Where the road from Davisville to Huntingdon intersects the county line, 
there is an extensive trap dyke running nearly E. and W. in a straight line for three miles. The 
gneiss in its vicinity assumes very much the character of a syenite, and some of it might be use- 
ful as a buildino--stone. 

The Eiver Schuylkill presents a series of excellent exposures of the different divisions of the 
gneissic belt, from Philadelphia to Spring Mill. The general structure of this part of the region 
is exhibited in No. III. of the larger sections. 

At Fairmount, near Philadelphia, the gneiss projects above the Diluvium, and is quarried to 
some extent in this vicinity, and also on the west bank of the river in several places. The 
grain or lamination of the rock is exceedingly contorted, implying the occui-rence, at some 
period, of an immense compressing force. In all the quarries from Fairmount to the Falls of 
the Schuylkill, the rock is intersected by numerous cross joints, which appear, until closely 
examined, to represent its divisional plains or true stratification, and which, at Fairmount, are 
nearly horizontal. These joints divide the mass into blocks of convenient shape and dimensions, 
and when they dip in the proper direction, greatly facilitate the operations of the quarry. The 
belt of felspathic gneiss which passes Philadelphia is well developed on Darby Creek, Crum 
Creek, Ridley Creek, Chester Creek, and the other adjacent streams. On nearly all of these it 
has long been wrought, supplying Philadelphia and other places with a large amount of very 
excellent working-stone, and material for the foundations of houses, and for other purposes. At 
the Falls of the Schuylkill there is a large quarry of very excellent gneiss of a light grey aspect, 
which has long contributed its supply of good building-material to Philadelphia. In this quarry 
there is a vein of large-grained granite, with red felspar ; the strata dip to the N.W. 

Falls of Sclmylkill Quarry. — The quarries at this locality expose the thick-bedded variety 
of gneiss, consisting of felspar, quartz, and black mica, with an occasional sprinkling of solitary 
crystals of garnet. The felspar and garnets show a tendency, especially in the upper layers, to 
partial decomposition. The stratum is traversed by numerous great joints, running approxi- 



SECOND BELT OF GNEISS. 



71 



mately N. and S. The direction of the dip is about 15° — 20° to N. 20° E. It tends to quarry 
in large irreguLar trapezoidal blocks. The mica in this rock is in minute scales, and small in 
quantity in proportion to the quartz and felspar. The lower quarry exposes a massive gneiss, of 
alternating mica and felspar bands, with tendency to a porpliyritic structure from excess of 
felspar. 

Second or Middle Belt. — The middle zone of the Gneiss of Southern Pennsylvania, as 
it crosses the Schuylkill, consists of an alternation of four principal varieties. Perhaps the most 
abundant of these is a very micaceous species of the ternary or mica quartz and felspar 
rock, holding garnets in greater or less profusion. A very common feature in this rock is a 
wavy or minutely undulated lamination, arising apparently from a contorted or wavy structure 
in the coarsely crystallised mica, its predominant mineral. This would seem to proceed from the 
interference of the innumerable planes of cleavage, or— what is the same thing — of crystalline 
lamination with the original planes of deposition of the strata. The twisted form of the flakes 
of mica is frequently seen to be due to the displacing effect of grains, or crystalline bunches of 
included quartz. It would seem as if these minerals had crystallised or segregated, from their 
parent sedimentary materials, under a conflict of forces, the newly-awakened crystallising energies 
being not always parallel to the original bedding of the deposit, but more frequently oblique to it. 

Perhaps the next most common subdivision of the gneiss of this middle tract is a variety 
consisting almost exclusively of the above-described wavy mica. This rock graduates into the 
more micaceous sorts of gneiss, by containing a less or greater mixture of finely-granulated 
crystalline quartz, felspar, and hornblende. The southern half of the gneissic zone before us 
is characterised, on the Schuylkill and the Wissahickon, by containing an alternation of the above 
two varieties of micaceous gneiss or mica-slate, with beds of hornblendic gneiss — the last- 
named rock being, from its thin lamination, sometimes entitled to the name of Hornblende Slate. 
The northern half of the zone consists largely of a fourth variety of the more schistose class of 
the gneissic rocks. This is a grey fine-grained binary mixture of granular quartz and minutely 
crystallised scales of mica, the quartz being the prevailing element. It is a species of whetstone, 
and some of the more quartzose bands would furnish masses well suited for employment as 
whetstones for scythes. A very common, indeed a characteristic feature of this quite remarkable 
and extensive division of the micaceous gneiss group, consists in its peculiar fracture ; the rock 
breaking into long narrow chunks, comparatively smooth on their sides, but excessively ragged 
on their ends ; a style of fracture strongly resembling that of half-rotted fibrous wood. This 
peculiar rock is in greatest force towards the northern side of the middle gneissic belt, or between 
the serpentine and steatite, and the hard felspathic gneiss of the southern margin of the third 
or Northern Gneissic Belt. It is interstratified towards its southern side, with more or less 
frequent and thick bodies of the other variety of mica-slate, possessing the mica in large and 
twisted scales, with an abundance of garnets. On its northern side it alternates to some extent 
with a greenish talcose slate, or, what is the same thing, the talc in this quarter replaces the 
mica in whole or in part in certain divisions of the group. 

It is here that we meet with the interesting belt of Steatite and Serpentine, which extends 
from E. of the Wissahickon on the brow of Chestnut Hill, across the Schuylkill to Mill Creek, 
beyond Merion Square. Viewing the steatite as a stratified rock of the mica-slate group, we 
may reasonably regard it as having been metamorphosed to its present composition and structure, 



72 



SOUTHERN ZONE OF GNEISS. 



by infusion of magnesian matter from the dyke of intrusive Serpentine which everywhere 
adjoins it. 

Wissahickoii Creel- Section, comprising the Talc-Slate, Steatite, and Serpentine. — This section, 
intended to illustrate the Middle Belt, commences at the most northern exposure of the mica-slate 
S. of Thorpe's Paper-Mill. The rock is a mica-slate, exceedingly full of garnets. Besides the 
mica, which is the principal constituent, and the garnets, it contains a little minutely disseminated 
quartz, but not much. The dip is 80° to S. The mica is everywhere more or less minutely 
wavy, and in the very micaceous kinds it is coarsely crystallised and remarkably waved. It 
weathers a ferruginous brown. 

The exposure of talc-slate, steatite, and serpentine, connnences opposite the bridge over 
Wissahickon Creek, near Thorpe's Mill. The first rock which here succeeds the gametiferous mica- 
slate above described, is a stratum of green talcose slate, estimated to be 40 feet thick ; this dips 
about 70° to N., about 20" W. Reposing upon it at the same angle is the Steatite Group, which 
is an alternation of talc-slate and talcose steatite ; the former material apparently predominating. 
This occupies an estimated breadth or thickness of 120 to 140 feet. In the northern half of this 
group the talcose chloritic beds contain numerous octahedral crystals of oxide of iron. 

Next in order N., and adjoining the Talc-Slate and Steatite, is the Dyke, or Bed of mixed 
Serpentine and Steatite. The thickness of this is not great, apparently not more than from 
12 to 20 feet. 

A steatitic Talc-slate adjoins the Serpentine on the N., extending for 30 feet. 

Then succeeds a Garnetiferous Mica-slate, dipping about 85° to N., 20° W., quite gametiferous, 
precisely similar to that below this. It dips as do the others, and extends for 75 feet. 

This is succeeded by a close-grained Quartz-slate or Scythe-stone, the thickness of which is 
about 100 feet. 

Following this is the ordinary very garnetiferous Mica-slate— mica in large flakes, and crinkled. 
This bed has a thickness of 50 feet. 

Next in order, extending for 500 feet, is a group of beds composed chiefly of a hard Quartzose 
Mica-slate, or thin-bedded Quartzose Gneiss, including alternating thin beds of the ordinary 
garnetiferous mica-slate. 

This brings us to a bold dyke of Bluish-grey Granite, from 50 to 60 feet in width. 

Then succeeds a hard Blue Micaceous Quartzose Gneiss or thin-bedded Flagstone. This alter- 
nates with the more rough mica-slate ; it has a thickness of about 200 feet. On the N. edge of 
the Quarry it seems to dip S. 85°, but towards its northern limit its dip is about 85° to N. 

Succeeding this rock is a belt of close Hornblendic Gneiss and Quartzose Mica-slate, having a 
thickness of 200 feet, its northern limit coinciding with a marked depression in the hills. These 
are the uppermost or terminal beds of the great gneissic formation. A spring of remarkably pure 
well-aerated water occurs in the Flagstone Group, a little N. of the Granite Quarry. 

Passing the depression in the hill, we enter immediately upon the Primal Older Slates in their 
usual metamorphic condition, with characteristic white streaks of imperfectly crystallised felspar 
and dark hornblendic mineral, and with the roundish specks of semi-crystallised felspar. One band 
in this formation is excessively hornblendic, very ferruginous, and may possibly include some 
workable iron ore. These rocks possess precisely the type which they exhibit on the Schuylkill. 
Their thickness on the Wissahickon Creek cannot be less than 300 feet ; dip about N. 20" AV. 



THIRD BELT OF GNEISS. 



No outcrop of the Barren-Hill White Felspar Rock could be detected at the base of the hill. That 
the Barren Hill opposite this point has an anticlinal structure, seems evident from the fact that 
the overlying limestone occurs on the S. slope of the ridge, close to the turnpike-gate on the city 
line, at the intersection of the Germantown and Perkiomen Turnpikes. Good brown iron ore is 
found in the Little Valley between the main hills of Gneiss and the Barren-Hill Ridge. 

I am inclined to infer, that upon the Wissahickon Creek this highest group occupies a 
narrow^er belt than upon the Schuylkill. 

Third or Northern Belt. — The third and most northern of the divisions into which 
we have found it convenient to separate the Gneiss of the Schuylkill district, extends from 
the somewhat abrupt cessation, or edge of the above-described micaceous belt, to the base 
of the Primal altered slates of the South Valley Hill, at Spring Mill. This zone is here, at 
the river, not more than about half a mile in breadth ; and what is curious, it runs to a point, 
before reaching the Valley of the Wissahickon, only two and a half miles to the eastward, 
being overlapped obliquely by the margin of the Palaeozoic rocks. From its tapered point near 
the Ridge Turnpike, this zone of hard gneiss expands regularly in*its course westward, until 
at Darby Creek, and beyond it, or in the vicinity of the Delaware and Chester County line, it 
has a breadth of about four miles. The materials constituting this northern tract are very 
similar to, if not identical with, those which compose the southern or Philadelphian one. If they 
differ from that, it is by possessing a less proportion of the more micaceous varieties of gneiss, 
and almost no mica-slate. The prevailing varieties in this tract are, first, a massive felspathic 
gneiss, some of it micaceous, and some of it like a stratified syenite ; and, secondly, a dark hard 
hornblende felspar gneiss, thinly laminated and strongly striped, when viewed in transverse 
section. The first-named, or more felspathic kind, is in some beds porphyroidal, and strongly 
resembles the gneiss above Philadelphia, and that at the Falls of Schuylkill. 

A remarkable feature in the northern or uppermost bands of gneiss on the Schuylkill, or those 
which next adjoin the base of the Primal series, is the possession of a less than usual completeness 
of crystallisation in the constituent minerals, the felspar, more especially, appearing to be less 
perfectly developed than common, and more in the condition of roundish or lenticular segregated 
lumps. In this circumstance, the gneiss here approximates somewhat to the structure of the 
lowest beds of the Primal series, which are also porphyroidal, but exhibit their metamorphism in 
a far lower decree. 

The following somewhat more detailed description of this Northern Belt of the Gneissic 
Rocks will serve to exhibit more fully the differences between it and the middle Zone, and its 
general agreement with the lower or more southern one. 

Description of the Northern or Upper Belt of Gneiss. — The northernmost belt of gneiss, or 
that commencing near the Quarry, half a mile S. below Spring Mill, and extending to the northern 
brow of the hills overlooking that locality, is distinguished from the next division of the Gneissic 
Formation to the south of it, by the prevailingly massive character of its bedding, its large excess 
of felspar, and comparative deficiency of quartz, mica, and hornblende. The mica seems to be 
next in abundance to the felspar ; it is generally black, and in very minute scales. The horn- 
blende element predominates most in the upper members of the group adjoining the AVilbam 
Penn Furnaces, where beds of true hornblendic gneiss alternate with micaceous felspathic layers, 
and with others more purely felspathic. This entire group contrasts strikingly with that next south 
VOL. L K 



74 



SOUTHERN ZONE OF GNEISS. 



of it, in the total absence of garnets, and of that excess of mica, or of mica and quartz, which so 
generally characterises the garnetiferous varieties. From the massiveness of many of its beds, 
and the regular parallelism of its structure, this rock is admirably adapted for quarrying ; the 
less contorted and disturbed parts of the formation being fit to afford an abundance of noble 
blocks of building-material of almost any dimensions. Two sets of joints traverse the strata, 
one perpendicular to the horizon, but nearly at right angles to the strike, no matter what the 
inclination of the dip ; the other approximately coincident with the strike, and for the most part 
nearly perpendicular to the plane of stratification. 

This rock displays a marked gradation of abatement, as we ascend from the lower to the upper 
members of the group, in the extent of segregation or crystalline separation of its constituent 
minerals. These, in the inferior beds, are almost invariably the felspar and mica, especially in 
separate parallel laminae ; and where the felspar is in excess, it occurs in large porphyroidal 
crystals. But in the middle and superior portions, while the general parallelism of the lamination 
is still retained, the laminte are finer and more commingled. The several mineral constituents 
are less coarsely crystallised, and any isolated felspar has the form of lenticular or ovoidal knots, 
showino; a lower, less advanced, stage of segregation. It would seem as if these highest members 

o ' "doc) o 

of the whole gneiss formation have experienced a less perfect and thorough metamorphism than 
the middle and lower masses. 

Structure of the Upper or Northern Belt of Gneiss. — Near the bend of the Schuylkill, the 
lower strata of this upper group, in a bluff hill one-third of a mile below the William Penn 
Furnaces, displays a true anticlinal flexure, and it is here, just on the anticlinal axis, that the more 
northern of two considerable veins of granite intersect these strata. From this axis northward 
for 3.50 feet, the beds dip very regularly at angles declining from 55° to 40°, towards N. 20° W. ; and 
for the next 800 feet their inclination is so gentle, that they may be described as horizontal. 
Such dip as they do possess is from the river towards the N.E. At the limit here mentioned, 
they exhibit a distinctly marked synclinal structure, rising with a gradually increasing inclination 
for the next 300 feet, and then immediately displaying for the following 600 feet across their 
strike a succession of remarkable contortions, presenting, on a small scale, several beautiful anti- 
clinal and synclinal folds. This brings us to within some 200 feet of William Penn Furnace, No. 2. 
Here the contortions appear to terminate ; and with the exception of a few very subordinate twists 
in the bedding, the strata stand almost perpendicularly throughout the next 1400 feet. This 
brings us to the northernmost limit of the whole Gneiss formation, or to a line about 1400 feet 
N. of the Old William Penn Furnace, No. 1. It is possible that one or two plications may 
exist in this space ; but with one exception, which is at the n orthern end of the Upper Furnace 
(No. 1), the prevailing dip is nowhere less than about 80" to either the N. or S. 

As an argument for the general unconformity of the Lower Primal Eocks to the Upper 
Gneissic group, I would call attention to the folded and contorted condition of the latter, 
and the very uniform, nearly vertical, dip of the first-mentioned. Another even more cogent 
reason for assuming such unconformity is the striking contrast which prevails in the law of 
flexure, of the two formations. The undulations of the gneiss do not belong to the Appalachian 
system of south-east-dipping axes planes, but exhibit a wholly different character, being either 
minute and local contortions, or wide gentle undulations, with comparatively moderate dips, 
which are for the most part to the N., and not, as in the other system, to the S. 



DETAILS OF THE GNEISS. 



75 



Subdivisions and Details of the Northern Belt of Gneiss on the Schuylkill. — Commencing at 
the point below the Granite Quany, S. of Spring Mills, at about 100 feet S. of the end of the 
long tangent in the Norristown Eailroad, occurs the most northern good exposure on the side of 
the railroad. It begins with a small injection of pinkish granite composed of felspar and quartz. 

Immediately adjoining the grauite on the N. side, we find a variety of massive gneiss, con- 
sisting of rather coarsely crystallised felspar, quartz, and hornblende, with some mica. Certain 
bands of it tend to the porphyroidal structure, from excess of felspar. It is evenly bedded, and 
shows the parallel lamination of gneiss, but this is not minute or very continuous. It dips about 
80° to N. 20° W. A similar massive gneiss appears to occupy the hill on the opposite side of 
the river, at the cuts in the Eeading Eailroad. 

About 160 feet N, of the first dyke is a second vein of granite, or more properly a syenite, 
producing, on the gneiss in contact with it and S. of it, a S. dip of 70°. This syenite is composed, 
chiefly, of coarsely crystallised felspar, both jjinkish and white ; it holds a much less proportion of 
quartz, and a considerable amount of large specks of imperfectly crystallised or finely granu- 
lar hornblende. The injection is about 10 feet thick. 

Succeeding the dyke of syenite, is a repetition of the kind of gneiss occurring to the 
southward, massively bedded, porphyroidal in many of its layers, of a bluish-grey colour, and 
consisting, for the most part of a triple mixture of felspar, quartz, and mica, and occasionally some 
hornblende — the felspar frequently appearing in large insulated blotches. This rock is now 
extensively quarried ; it occupies the bold point of the hill, causing a bend in the river. From 
the vein of syenite, for 2.50 feet across the strike, it dips very evenly at an angle of 45° or 50° to 
N. 20" W. But at that distance the dip changes pretty suddenly to a very small angle. On the 
side towards the syenite it is penetrated by a few injections of granite. It would thus seem that 
there is here a true anticlinal flexure in the gneiss — a large vein of syenite being protruded very 
nearly in the axis. The slight northward dip is succeeded at about 900 feet from the Quarry by 
a gentle dip to the S. 

Some 387 feet N. of the Small Quarry, at the S. end of the New Furnace (William Penn Fur- 
nace, No. 2), the rock is seen in a cut made for pumps ; the dip is almost perpendicular, about 87° S. 
It is a good exposure of a quite peculiar gneiss, massive, dark-blue, streaked, and lenticularly 
spotted white. It consists chiefly of felspar and dark-blue mica, in alternate slightly wavy bands 
or laminae, with lenticular concretions, or crystallisations of pinkish- white felspar. Some of the 
beds are porphyroidal, from abundance of lumps of felspar, others minutely or closely laminated 
in delicate parallel, slightly wavy, bluish-black and pinkish- white streaks, produced by the two 
predominant minerals. This rock contains some quartz, and occasionally some hornblende. Its 
vei-tically dipping beds support the large New Iron Furnace, No. 2. 

At the N. end of the New Furnace is a felspathic micaceous gneiss, somewhat minutely 
banded, without the lenticular crystallisations of felspar. 266 feet from the N. end of the 
New Furnace is a trap-dyke, very hornblendic, about 8 feet thick. 

About 421 feet N. of the north end of the New Furnace is the same kind of gneiss, minutely 
streaked or laminated, some beds still containing lenticular segregations of felspar, but these fewer 
and smaller, the whole rock more minutely and evenly laminated, and more closely resembling an 
altered argillaceous sandstone, yet still claiming the appellation of a gneiss. The felspar has a 
mealy chalky aspect on the weathered surfaces. 



76 



SOUTHERN ZONE OF GNEISS. 



About 100 feet N. of the north end of the Old Furnace, No. 1, is an exposure of a felspathic 
micaceous gneiss, which continues for 170 feet. At the north end of this furnace the dip is 60°, 
but 100 feet farther on it is 85°. 

Nearly 330 feet N. of the north end of No. 1 Furnace, there is a ledge of a somewhat different 
rock, with almost perpendicular and regular bedding. Decidedly less gneissic in its crystallisa- 
tion, it has lenticular lumps of felspathic mineral, and is finely streaked ; the whole has an earthy 
sedimentary aspect, and the felspathic specks and concretions are rounder than in the true gneiss; 
the strike of the rock is nearly S. 70° W., or parallel with the prevailing strike of the genuine gneiss ; 
to the southward its course is such as to range straight for the shore of the river at the Ferry House, 
opposite Spring Mill, and it must range thence along the north base of the belt of hills bounding the 
river, between the Ferry House and Merion Furnace, opposite Conshohocken. This rock has a more 
earthy and less crystalline aspect. I incline at present to regard it as the lowermost member of 
our Secondary or Palaeozoic system of strata. If it be really such, it is not here locally separated 
from the gneiss beneath it, by any marked unconformity in respect to either their strike or dip, 
but the two sets of rocks are contrasted in a very marked manner, both in their external aspects 
and their mineral composition. The passage from one into the other is so abrupt as regards their 
composition and crystallisation, as to require us to place them in wholly different systems. The 
visible thickness of the vertically-dipping beds of this upper doubtful group is about 100 feet. 
This stratum forms the N. point and face of the hill, immediately S. of the Spring-Mill Valley. 

Limits of the three Belts of Gneiss of the Southern Gneissic District, more i^recisely defined. — 
It is not possible to trace, at least at present, with close precision, the boundaries eastward and 
westward which separate the southern and northern belts of harder gneiss, from the middle tract 
of softer, or more micaceous strata ; but their approximate limits may be indicated somewhat as 
foUows : — 

Limits of the Southern Belt. — The Southern, or Philadelphia Belt, can be traced from the 
Delaware, below Trenton, to the Neshaminy, constituting the whole of the gneiss S. of the 
southern edge of the red sandstone. West of the Neshaminy, its northern border, or that which 
separates it from the micaceous middle belt, leaves the southern trough of Primal white sand- 
stone, and, trending south-westward, passes between Shoemaker Town and Mill Town, and 
crosses the Schuylkill near the northern side of Manayunk. To the S.W. of the Schuylkill the 
limit is less precise, partly from a deficiency of exposures of the rocks, and partly — perhaps 
chiefly — from the existence of a succession of undulations, which may cause a repetition of out- 
crops, or separate belts of the two divisions of the strata. On the Brandywine, the northern 
limit of the more massive gneiss would appear to be somewhere N. of Chadd's Ford. It would 
seem that, after crossing the Brandywine, the rocks of this group run forward for several miles, 
into Chester County, and through the northern side of Delaware into Maryland, in a succession 
of gradually contracting ranges or slender fingers, the more northern of which terminate in the 
neighbourhood of the Eedclay and Whiteclay Creeks, while the middle ones extend forward to 
cross the Little Elk Creek, and to pass to the south of the eastern end of the great Southern Belt 
of the Serpentine. It is very obvious, from the structure of this zone on the Brandywine, from 
Chadd's Ford, southward, and through the country to the west of that stream, that the gneiss is 
here undulated in a series of wide anticlinal waves. This is indicated, not only in the alternately 
N. and S. dips of the strata on the Brandywine, but in the occurrence of those several synclinal 



NORTHERN LIMIT OF SOUTHERN GNEISS. 



77 



troughs of Primal and Auroral palaeozoic rocks, which in the south-eastern corner of Chester 
County, and the north-eastern corner of the State of Delaware, are folded in between the uplifts 
of the gneiss. Besides these anticlinal fingers, this southern gneissic belt sends forward to the 
S.W. a long unbroken zone or line of outcrop, through Northern Delaware and Cecil County, 
Maryland, to cross the Susquehanna Eiver between a point some two miles below the Pennsyl- 
vania State line and Havre-de-Grace. This is a grey granitoid gneiss, composed largely of 
quartz and felspar, and occurs on the Susquehanna in very massive beds. 

Limits of the Mica Slate or Middle Gneissic Belt. — Viewing the middle micaceous belt as 
terminating eastward, somewhere in the neighbourhood of the Neshaminy, and S. of Edge 
Hill on the southern ridge of Primal sandstone, we can define its northern limit to be formed by 
that outcrop of Primal rocks passing Moretown and Chestnut Hill, to a point a little W. of the 
Wissahickon, at which latter place the mica-slate seems to leave the belt of Primal rocks, and to 
be bounded thenceforward on its north-western side by the south-eastern margin of the northern 
tract of older felspathic gneiss. Thus limited, it crosses the Schuylkill, as already defined, about 
one mile S.E. of Spring Mill. From the Schuylkill the line of contact of the two groups, pursu- 
ing first a course somewhat W. of S.W., passes through the eastern corner of Haddon Township, 
and the lower edge of Newtown, to take a range somewhat more to the W., coincident nearly 
with the north-western edge of Delaware County. It then proceeds through Westtown, in 
Chester County, and crosses the Brandywine somewhere within a mile below the E. and W. 
branches of the junction of that stream. East of Unionville the tract of hard felspathic and 
hornblendic gneiss, to the N. of the more micaceous gneiss, appears to run to a point, and here, 
therefore, the common boundary of the two groups re-curves rapidly backward towards the N.E. 
Whether the rocks bounding this belt of harder gneiss, W. of the Brandywine, appertain all of 
them to the ancient Gneissic slate formation, or whether they are not in reality the lower Primal 
slates under a highly metamorphic and crystalline condition, is a question which remains open 
to future research ; but I incline to the belief that, within the general synclinal trough of the 
micaceous gneiss, where the Brandywine intersects it, we shall ultimately discover smaller 
synclinal waves, containing unconformable troughs of those older Primal slates. The western 
general limit of the middle gneissic belt may be vaguely defined, then, as occurring somewhere 
near the Brandywine, across which it is probable there extend some narrow anticlinal fingers, 
expiring, like those of the southern harder gneiss, under the overlapping, very undulating, 
margin of the altered Primal series. "Whether, indeed, there may not occur, even in the more 
central tracts of this micaceous zone, between the Schuylkill and the Brandywine, some small 
insulated troughs of the Primal older slates, is a point which likewise remains for future 
investicration. 

Limits of the Northern Belt of the Southern Gneissic District. — We have just defined, 
in a general way, the southern boundary of this northern tract of gneiss, and it remains 
to describe now its northern edge, or that which separates it from the long continuous belt 
of Primal talcose older slates which border it on the N. From a little W. of the Wissahickon, 
where this northern tract of gneiss seems to emerge from under the Edge Hill trough of 
Primal strata, the common limit of the gneiss and talcose slate can be readily traced 
along the northern brow of the Chestnut Hill range, to the Schuylkill just below Spring 
Mill. West of the Schuylkill, the line of contact of the older Primal, with the Gneissic strata 



78 



SOUTHERN ZONE OF GNEISS. 



ranges along the brow of the range of hills overlooking the river, and thence through the summit 
of this ridge, as it borders the limestone valley of Merion Furnace. It thus passes G. W. 
Fisher's, and P. Pechin's, and W". Morgan's, N.E. of Morgan's Corner. Thence its course takes 
it about half a mile S. of the Spread Eagle Tavern. On the back road from the Paoli to the 
Spread Eagle, S. of the turnpike road, we find the limit of the two formations, about one-third of 
a mile E. of the cross-road leading from Reeseville to the Leopard Inn, a dyke of close-grained 
bluish trap-rock occurring a little N. of the line of junction. Here the older rock is a dark 
bluish grey felspathic micaceous gneiss, very similar to that S.E. of Spring Mill on the 
Schuylkill. In this vicinity, further eastward, the gneiss is very quartzose and massive. It 
dips 85°, to N. 10° E. In the deepest of the railroad cuts, near the Toll-gate, W, of Morgan's 
Corner, the rock is a massive granitic gneiss, of greenish felspar, white and garnet-coloured 
quartz, and brown mica. These varieties are here cited, for the purpose of comparison with the 
very different kinds of gneiss, which we will presently find to prevail in contact with the Primal 
slates further westward. Tracing the edge of the gneiss, it may be seen to pass about one mile 
and a half S.E. of the Paoli, or half a mile N.W. of the Leopard Inn, on the Darby Road. Here 
the rock is a more hornblendic gneiss than further eastward, and the change from this- hard 
material, to the softer talcose micaceous Primal slates, is plainly visible in the transition from a 
somewhat uneven surface to one of a lower level, having smoother outlines and softer undula- 
tions. Our line now crosses Crum Creek, near Mavis's Grist Mill ; and here the gneiss is in close 
proximity to the southern margin of the long belt of stratified serpentine, which originates in 
the talcose primal slates, about one mile S.E. of the Paoli, and more than one-fourth of a mile 
N. of the gneiss at that point. From Crum Creek, where a very hornblendic gneiss commences 
and ranges for many miles south-westward, its northern or north-western edge, coincident nearly 
with the southern border of the serpentine as far as Taylor's Run, passes about one mile N. of 
Sugartown, and the same distance N.W. of West Chester. Following the southern side of the 
valley of Taylor's Run, till it approaches the Brandywine, it crosses this stream below Taylor's 
Ford, and preserves its course westward to the vicinity of Marshallton, keeping near the road 
leading from West Chester to that village. In the vicinity of JMarsliaUton and TrembleviUe this 
line seems to terminate, or to deflect rapidly southward ; for the north-western, or here, western 
boundary of the true gneiss, appears not to reach as far to the westward as the village of Union- 
ville, in East Marlborough Township. 

Of the Geological Structure of the Gneissic Region of the Schuylkill — {See the Section.) — A 
remarkable feature in the structure of the whole southern gneissic district, is the prevalence of a 
northward dip in the strata. This inclination prevails along the Schuylkill, with very few local 
and trivial exceptions, throughout all the three great subdivisions of the zone of gneiss, until we 
approach the upper or northern side of the third or northern belt. There the rocks for the first 
time, for any considerable width of outcrop, are contorted, folded, and lifted into a generally 
almost perpendicular dip. The ordinary or average angle of inclination of the strata may be stated 
to vary between 30° and 50°, and the prevailing point of the compass to which this dip is directed 
is somewhere between N. 20° E., and N. 30° E., though occasionally it is nearly N., and in one or 
two instances it is N.E. From Philadelphia, the whole way to the AVissaLickon, there exists no 
interruption to this general northward dip, and not until we approach the lower edge of IMana- 
yunk is it much undulated or contorted, and even there the undulations are within very narrow 



STRUCTURE OF GNEISSIC REGION. 



79 



limits, and produce very little reduction in our estimate of the thickness of the formation. At 
Fairmount the true dip of the rocks is very steep, approaching, indeed, to the vertical. The 
strata there are traversed by numerous conspicuous joints, presenting at a little distance a decep- 
tive appearance of a nearly horizontal stratification, in thick and almost parallel beds ; but this is 
not to be confounded with the genuine stratification or grain of the rock, as marked by the 
structural distribution of its mica and other minerals. 

Advancing northward, this steep inclination of the strata soon subsides, for along the shore 
of the river, from Lemon Hill to the Quarries below the Columbia Bridge, the ruling dip is in 
only one or two local spots steeper than 40°, or even than 30°. In the Quarries spoken of, it is 
in one or two places 50°, and even 70°. From the Columbia Bridge to the Wissahickon, and 
even beyond it, the rocks dip with remarkable steadiness at angles seldom lower than 20°, and 
seldom higher than 30°. Passing the Wissahickon, they begin to exhibit a series of local contor- 
tions, though but few of these contain a dip to the southward for more than a few yards. At 
two or three spots below Manayunk, the inclination is as steep as 50°, or even 70°, but at 
the town, and indeed as far up as the Sinnaminson Creek, a quite gentle slope prevails, the 
highest angle not exceeding 20° or 25°, excepting at one locality of very narrow contortions . 
Above the Sinnaminson, as far as the Greentree Run, the dips are a little more variable, and 
generally steeper, but nearly all are embraced between the angles of 30° and 50°. In this part 
of the section the strata are more waved in their dip, though never thrown out of their prevail- 
ing northward declination. Approaching and passing the Greentree Run, we find them through 
a space of nearly 300 feet in an almost perpendicular attitude ; they soon, however, resume their 
dominant northward dip ; but from this point to the vicinity of the Soa|)stone Quarry, they pre- 
sent, for the first time, a succession of synclinal and anticlinal undulations. In this division of 
the section, the inclination of the strata — still to a large extent towards the north — is at all 
angles from 30° up to 70°. It is worthy of note here, that the steatite belt itself gives evidence of 
containing a synclinal wave in the dip ; for the talc-slates and mica-slates to the south of it, for 
several hundred yards, dip steadily towards the north, at an angle of about 30°, while those of the 
northern side of the Quarry show a steeper inclination to the south. Passing the Steatite Range, 
the northward dip is quickly resumed, and in this part of the Mica Slate Belt, both at the Schuyl- 
kill and on the Wissahickon, the slope is steeply towards the north. 

Entering now that division of our section which belongs to the Northern Belt of harder 
Felspathic Gneiss, we encounter the most irregularly dipping or undulating portion of the whole 
gneissic zone. Approaching the Quarries of Blue Porphyroidal Gneiss, at the lower limit of this 
tract, we meet with a steeply-compressed anticlinal axis in the strata, the line of the axis 
marked by a strong dyke of syenitic granite. Here the south dips are 70°, and even steeper, 
while the north ones vary from 45° to 55°. Passing the Quarries, we immediately encounter a 
wide space of more than a fourth of a mile, in which the rocks are almost horizontal, and towards 
the northern edge of this we perceive an axis or turn in the dip, marking a broad, regular, syn- 
clinal trough or basin. From the northern edge of this trough, to the upper limit of the whole 
gneiss formation, past the Wilham Penn Iron-Furnace, No. I., the gneiss is closely folded, and 
compressed into very steep, or nearly perpendicular dips, with numerous short plications. 

If now we review these interesting features in the structure of this broad zone of gneiss, we 
can hardly resist the conclusion, that in the three belts passed over by our section, there are 



80 



SOUTHERN ZONE OF GNEISS. 



really but two groups of rocks, a lower and a Ligher, and that the entire zone, viewed broadly, 
constitutes but one wide synclinal wave or basin, the harder felspathic and hornblendic gneiss 
dipping northward, throughout the whole southern belt or outcrop, and reappearing in steep and 
multiplied contortions on the other side of the trough, and the upper or more micaceous group 
of rocks filling the synclinal centre of the trough, and compressed into the lesser foldings which 
it exhibits, by the lateral force of the W' ide crust undulation, within which it has been caught, and 
folded. 

Of the Belt of Gneiss North of the Mooretown and Attleborough Range of Primal Sandstone. — 
Between the southern edge of the Middle Secondary or Mesozoic red sandstone formation, in 
Bucks and Montgomery counties, and the southern range of Primal white sandstone, extending 
from Edge Hill to Morrisville, there is a nearly continuous long and narrow tract of Gneiss rocks, 
which in their composition seem to be identical with those of the northern belt, west of the 
Schuylkill. Indeed, from the fact of this identity, and from their lying in the same line of 
strike, the rocks of the two tracts must be regarded as belonging to one continuous zone of 
strata, interrupted at the surface only by the basins of the older Palseozoic strata, which lie 
obliquely across the belt. It is not necessary to define it minutely in this place, further than to 
add to what has been now indicated, the statement, that at the western end of this area the 
gneiss runs forward in three points. The first and longest projecting finger of the belt is a con- 
tracting anticlinal outcrop, which is insulated from the middle finger by the narrow synclinal 
trough of Primal rocks, which passes the Pennypack Creek at Shelmire's Mill. From the Penny- 
pack, where it is rather more than a mile wide, this promontory of the gneiss ranges contracting 
in width, between the southern foot of Edge Hill and the northern border of the Mooretown and 
Attleborough range of Primal strata, until, south of the village of Edge Hill, it has a breadth not 
exceeding one quarter of a mile. Within a mile to the W. of this place it runs to a point, 
being saddled by the Primal slates and wdiite sandstones of Edge Hill, or the eastern extension 
of Barren Hill. This is evidently an anticlinal elevation in the gneiss, and the axis is a very 
straight one, and of considerable length, being prolonged even to the Schuylkill, a distance of 
several miles beyond the point at which the gneiss itself sinks out of sight. 

The middle branch or finger of this area of gneissic rocks is much shorter than either the 
southern one, just traced, or the most northern, presently to be mentioned. It extends for about 
two miles westward of the Huntingdon Turnpike, to a point about one mile west of the Penny- 
pack, or to within three-fourths of a mile of Willow Grove. It is an anticlinal belt, embraced 
between the southern and northern synclinal ranges of the Primal sandstone, into which the 
eastern end of the limestone basin of Montgomery County forks. This gneiss may be seen on 
the Pennypack for about half a mile above Shelmire's Mill, and is again intersected, near its 
western termination, by the road leading south-eastward from Morgan's Mill to Blaker's Store. It 
terminates in a point about due south of Morgan's Mill. 

The most northern branch of the belt of gneiss rocks before us is in reality not continuously 
connected with the main tract, but is cut off' from it by the encroachment of the southern edge 
of the red sandstone against the northern prong or basin of Primal white sandstone, in the vicinity 
of the Pennypack. The denudation of the red sandstone, AY. of the Pennypack, and N. of 
Willow Grove, has exposed this patch of the gneiss through a length, bordering the northern side 



DETAILS WEST OF THE BRANDYWINE. 81 

* 

of the Campliill outcrop of Primal rocks, for as much, as four miles, and through a breadth, on 
the Doylestown Turnpike, amounting to about one mile. 

Throughout these three western branches of the northern belt of gneiss, the strata are of 
the same hard massive character as those which constitute the northern tract W. of the 
Schuylkill, and S. of the Chester County Valley, and there can be no doubt that they are a 
prolongation of that range. The predominant varieties are hornblendic and felspathic gneiss, • 
with a subordinate proportion of beds of the more micaceous kinds. 

Old Plumbago Mine, Buck's County. — Near the Buck Tavern, on the New Hope Turnpike, 
there is an old mine of plumbago on the farm of Isaac Hogeland. A tradition states that black- 
lead was procured here more than a hundred years ago. After lying long neglected, the mine 
was recently reopened, but it is again in a state of dilapidation, and no accurate observations 
respecting the vein or bed are at present practicable. 

NAEKOW EANGES AND LOCAL OUTCROPS OF GNEISS WEST OF THE 

BRANDYWINE CREEK. • 

Southern Belt. — Commencing our description of the more detached tracts of the harder horn- 
blende and felspar varieties of gneiss, constituting the general Southern Belt of the Southern 
Gneissic Eegion, where they begin to separate into anticlinal fingers, W. of the Brandywine 
Creek, the first band we have to notice is one which crosses that stream in the vicinity of 
Chadd's Ford. This runs towards the western end of Pennsbury Township. The principal 
variety of the rock at Chadd's Ford is a dark blue and speckled hornblendic gneiss. This 
anticlinal outcrop seems to end within two miles of the river, but, in the same line of strike, a 
rock of the same composition is uplifted through the newer strata, in two or three detached 
broken ridges, all the way to the East Branch of Redclay Creek at Pierce's Paper-Mill. It is 
probably an extension of the same anticlinal range. 

As already mentioned, the Gneiss Rocks basin a little below Chadd's Ford, and in the line of 
this basin, rests, further westward, a trough of crystalline Auroral limestone, with some Primal 
sandstone. South of this trough, a much broader tract of the gneiss branches forward toward 
the W., bounding the Kennet Square Basin of Limestone and its eastern branch, on their south. 
This belt embraces both hornblendic gneiss and the ordinary grey felspar and mica rocks, the 
latter being sometimes quite micaceous and full of large garnets. 

Approaching the East Branch of Whiteclay Creek, this tract of gneiss begins in turn to 
subdivide, and at the intersection of that stream it breaks up into three narrow tapering fingers, 
apparently subsiding anticlinal outcrops, which terminate at, or a little to the westward of, the 
Middle Branch of Whiteclay. The most northern of these bands crosses this stream a little 
below Moor's Grist-MiU, the middle Fork reaches it about Wickersham's Mill, and the southern 
crosses it to the southward of Pennock's Factory, to extend apparently nearly one mile further 
westward. Between these narrow subsiding belts of the gneiss lie narrow troughs of micaceous 
and talcose slate, identical, in crystalline and other characters, with similar rocks further N, 
which I have unhesitatingly referred to the Primal Slate series. The predominant rock in these 
narrow outcrops of gneiss is the hornblendic variety. 

VOL. I. L 



82 SOUTHERN ZONE OF ONEISS. 

• South of the detached fingers of gneiss above described, runs a much more extended and 
broader tract of the same rock, across the Whiteclay Creek above its forks. The northern edge 
of this passes the little manufacturing village of Chandlerville, on the East Branch of Whiteclay, 
and its southern border adjoins the narrow ba^in of crystalline limestone which includes Nevin's 
Quarries. This belt stretches towards Keniblesville. 

At the main fork of Whiteclay Creek, and for half a mile N.W. of this, we have the broken 
outcrop of tlie gneiss, some of the beds of which are of the prevailing hornblende variety. This 
bounds the trough of limestone on the S.E., and it ranges south-westward into the N.E. corner of 
Maryland. 

Middle Belt of Gneiss on the Brandytvine. — Turning next to the middle tract, or that of more 
micaceous gneiss, we may state briefly, that wherever it displays itself on the Brandywine above 
Brinton's Ford, or between Brinton's Ford and the main fork of the stream, it is a somewhat 
decomposable rock, consisting of the ordinary triple mixture of quartz, felspar, and mica, with 
some strata of thinly-bedded hornblendic gneiss and numerous layers of very micaceous gneiss, 
full of large garnets. In this group occasionally occur thin bands of a granite-like gneiss, 
disposed in very regular parallel beds, and having a square fracture, which confers on it an aspect 
and structure resembling the white Primal sandstone when greatly altered. This gneiss much 
reseml)les some members of the formation Ijetween Fairmount and Manayunk. Many contortions 
occur in this zone on the Brandywine, but the prevailing dip is chiefly to the S.E. 

Northern Belt of Gneiss near the Brandywine. — A very similar rock to that just described as 
occurring below the forks of the Brandywine, occurs in the vicinity of Taylor's Ford, and west- 
ward from the river towards Marshallton and Trembleville. I conceive it to be not at all 
improbable, that the northern zone of more massive gneiss, in passing West Chester, subsides 
towards or beyond the Brandywine, and is there saddled over and swept round by the newer 
group of more micaceous felspathic gneiss, here interposed between the hornblendic variety and 
the talcose Primal slates. This, at least, is the most feasible view we can adopt, from the defective 
data afforded, after a diligent and careful study of the district. The stratification and composition 
of the strata are necessarily so obscure from extensive metamorphism,.and from the occurrence of 
many imperfectly traceable anticlinal and synclinal undulations, that it is next to impossible to 
define sharply the respective limits of the formations. 



CHAPTER II. 

MIDDLE ZONE OF GNEISS, 

OR THE GNEISSIC ROCKS BETWEEN THE NORTH VALLEY HILL OF CHESTER COUNTY AND THE 
SOUTHERN MARGIN OP THE MIDDLE SECONDARY RED SANDSTONE. 

Boundaries. — Having described the Gneiss, S. of the limestone basin of Montgomery and 
Chester, and of the red sandstone in Buck's County, in its several belts and outcrops, and under 
its different aspects, we come next to the interesting area of the same rocks W. of the 
Schuylkill, and between the North Valley Hill, as a southern boundary, and the southern margin 
of the Mesozoic red sandstone and the base of the Welsh Mountain as its northern. From a 
spot about half a mile west of Valley Forge as its eastern point, the southern edge of this broad 
belt of gneiss ranges continuously, along the northern Ijase or side of the North Valley Hill, in a 
direction about S. 70° W., the whole way to the Western Branch of the Octorara in Lancaster 
County. The northern, or rather the north-eastern boundary, formed by the southern overlapping 
edge of the red sandstone, is a gently curving line, commencing at the eastern point near Valley 
Forge, already designated, and terminating at the eastern end of the Welsh Mountain near 
the county line, between the counties of Chester and Berks. Traced in detail, it passes 
Wheatley's Lead- Mine near Pickering Creek, crosses that stream at Kenzie's Mill, and then, witli 
a gentle sweep convex south-westward, it passes immediately by the little village of Kimberton. 
From this point its course is nearly straight to Coventry Village, opposite the junction of the two 
branches of French Creek. It crosses, in this course, the main French Creek about two miles 
N.W. of Kimberton, and follows thence to Coventry the north side of the French Creek Valley, 
except at one bend of the stream opposite Pughtown, where the line for half a mile takes the 
southern side. From Coventry Village, the boundary between the gneiss and red sandstone, 
trending first a little N. and then slightly southward, runs nearly due westward for more than 
seven miles, to the north-eastern point of the main ridge of Welsh Mountain near the village of 
Springfield. But there is an insulated belt of the gneiss situated a short distance to the N. of 
this boundary, on the North Branch of French Creek, and this may l)e more strictly viewed as the 
northern extension of the formation. 

The north-western limit of the wide tract of gneiss before us, is traceable from the sources of 
Pine Creek, a tributaiy of the North Branch of French Creek, south-westward along the south- 
eastern base, first of the eastern spur of Welsh Mountain to Springfield, and from thence along 
the base of the main Welsh Mountain, over the I^ancaster County line N. of the little village of 
Cambridge, to within two miles of the western end of the ridge. 

Viewed broadly, this whole area of the gneissic rocks divides itself westward into two main 
spurs or broad fingers, the shorter and more northern one terminating at the point just indicated, 
some two miles E. of the western end of the Welsh Mountain ; while the southern, and much 
longer, extends forward between the North Valley Hill, and the southern base of ]\Iine Eidge, to 
the North-west Branch of the Octorara, already stated as the westernmost limit of the whole 



84 



MIDDLE ZONE OF GNEISS. 



tract. This division of the gneissic area into two western branches is the result of two 
wide anticHual undulations, and the reception between them of a broad synclinal belt of the 
Primal strata, penetrating the gneissic region eastward from the head- waters of the Pecquea in a 
gradually contracting basin, extending as far as the North Branch of the Brandywine in West 
Nantmeal Township. This synclinal belt of Primal rocks, a prolongation from the limestone 
basin of the beautiful and fertile Valley of the Pecquea, is itself a complex trough, penetrated from 
the eastward by two narrow anticlinal spurs or fingers of the gneissic rocks, causing it to branch 
into three subordinate troughs. The gneiss may therefore be described as throwing, towards 
the W., two large and long anticlinal belts, and between these, two others, much shorter and 
narrower. These latter start off from the main southern division in the neio-hbourhood of the West 
Branch of Brandywine, and extend for a few miles a little S. of W., the southern one to a point 
about one mile E. of the little village of New Italy, and the northern one to about two miles E. of 
Compassville. 

The relations of the geological structure of this district to its topography are such, that the 
gneissic rocks for the most part constitute the valleys, while the Primal strata form the ridges 
between them ; the one material being easily eroded, and the other, consisting mainly of hard, 
firmly cemented, and even semi-vitreous sandstone, opposing a superior resistance to the exca- 
vating action of the waters which shaped the surface. 

To define now somewhat more exactly the limits of the two principal ranges of the gneiss, 
or what is the same thing, the southern limit of the Northern belt, and the northern limit of the 
Southern one, we may state that the first line commences at the West Branch of Brandywine, 
near Ackland's Grist-Mill, and running almost due westward, follows the south side of the South 
Branch of Indian Eun, leaving the Manor Presbjrterian Church to the S. of it about half a 
mile. Thence, after crossing the West Branch of Brandywine, near M'^Dufi's Grist-jMill, the 
boundary between the formations coincident, nearly with the north base of the barren ridge of 
Primal white sandstone, extends along the south edge of the vaUey of Twolog Eun, beyond which 
it crosses the county line about one mile and a half S. of the village of Cambridge ; and now 
deflecting northward, and in one mile more, turning again westward across the Pecquea, it runs 
for three miles further towards the W. end of the Welsh Mountain, to unite with the north- 
western boundary of the same area of gneiss, already indicated as ending at this point. This 
wide finger of the gneissic district is bounded, in its western portion on its southern side, by a 
narrow belt of Primal sandstone and slate, separating it from the limestone of the basin of 
the Pecquea. 

Turning now to the northern limit of the Southern or longer belt of the gneiss rocks, we 
may approximately define it as crossing the West Branch of the Brandywine, near Waggon 
Town, and as extending thence towards the W.S.W. along the northern side of the valley of 
Eock Eun, till it crosses Buck Eun north of Morris's Grist-MiU, or more than half a mile N. of the 
E. Sadsbury Friends' Meeting-House. Thence it ranges more nearly westward, to the vicinity of 
the Mine Hill Gap, passing near the Black Horse. From the Mine Hill Gap, the line, coincident 
throughout nearly its entire length with the southern base of Mine Eidge, pursues a direction 
somewhat more southward, till it passes Copper Mine Eun in the vicinity of the old copper mine, 
from which the Mine Eidge derives its name. Beyond this point, to the western extremity of 
the visible zone of gneiss, the northern boundary observes a course very nearly towards the S.W. 



GNEISS NORTH OF CHESTER VALLEY, 



85 



It unites with tlie southern limit a little W. of the North-west Branch of Octorara Creek, where 
the belt of gneiss thus bounded ends in an acute point, enclosed by the North Valley Hill and 
the southern spurs of the Copper Mine Eidge. 

There remains to be described only one other subordinate tract of these gneissic rocks, that 
of the Northern Branch of French Creek. This is insulated superficially from the main area of 
the gneiss by a long narrow tongue of the Mesozoic red sandstone, and its dykes and ridges of 
trap-rock extending from Rock Eun, where it forks away from the main area of red sand- 
stone, and runs westward to the County line just N. of Springfield. The narrow strip of 
gneissic ground thus cut off from the main country of gneiss, by the above-mentioned tongiie of 
sandstone, commences in a point near Eock Eun, spreads to a width of nearly a mile N. of the 
Warwick Iron-Mines, and then contracts again, passing the Hopewell Iron-Mines, till it ends in 
its western point N. of Springfield. This insulated outcrop of ancient gneiss is an exceed- 
ingly interesting mineral zone. It includes those well-known, remarkable, mineral localities 
familiar to the mineralogists of the State, as the Knauer Town Copper-Mine, Steel's Iron Pits, 
and the Iron-Ore Mines of the Hopewell Furnace, all of which will receive a sufiiciently detailed 
description in a future chapter. 

Character of the Gneiss Rocks N. of the Chester County Valley. — A marked difference is 
presented between the gneissic region N. of the Chester County Valley, and that already 
described lying S. of it. In the latter district there occurs, as we have seen, a great diversity 
in the composition of the rocks of the older metamorphic class ; there being an abundance, if 
not a prevalence, of the softer micaceous varieties, and a general deficiency of the more massive 
granitoid kinds. Here, on the other hand, Ave encounter chiefly the granite-like varieties of white 
felspathic gneiss, with hard hornblendic gneiss, such as constitute the typical gneiss rock of the 
central ridges of the South Mountain, or Highlands between the Delaware and the Schuylkill. 
By far the most prevalent variety is a felspar-quartz rock, of a greyish white colour, holding 
only a subordinate amount of mica, and disposed in comparatively massive beds. Certain of the 
more minutely granulated sorts, of a whitish aspect, resemble so nearly some portions of the 
Primal white sandstone when excessively crystalline from metamorphic action, that to discrimi- 
nate between the two formations is by no means easy, but demands the closest care. Nor is this 
to be wondered at, for the composition of the white Primal sandstone is often just such as would 
be derived from a white felspar and quartzose gneiss of this description. Micaceous gneiss does 
occur in the area before us, but nowhere in outcrops of any considerable breadth ; and true 
mica-slate — except merely in thin subordinate layers — has been nowhere met Avith. Towards 
the northern side of the remon there would seem to be a laro-er relative amount of massive hard 
hornblendic gneiss, while centrally, and along the southern border, the white felspathic sort is 
by much the most abundant. 

Of the Undulated Structure of the Gneiss District, N.of the Chester County Valley. — That the 
wide area of gneiss now under description is undulated in a succession of anticlinal and synchnal 
waves, is obvious to any practised geological observer who studies its structure with due care. 
Indeed, the evidence furnished l^y our map and sections is even more conclusive, as regards this 
feature, than it is for the gneiss region south of the Limestone VaUey, for in that district the 
closely folded and convulsed condition of the strata renders the detection and tracing of the 
anticlinals of the gneiss extremely difficult, while here the undulations are, in the main, more 



86 



MIDDLE ZONE OF GNEISS. 



open, symmetrical, and susceptible of continuous tracing. Along the northern or north-eastern 
border of the district, especially S. of the Valley of French Creek, the topographical features, of 
themselves, plainly suggest the presence of a succession of anticlinals. The present margin of 
the red sandstone marks pretty evidently the approximate ancient shore-line of that wide estuary, 
which floated the sediments to form the red sandstone ; and this shore-line was determined by 
the northern sides, and eastern ends, of a succession of hills or anticlinal ridges, which kept oif the 
waters from the country further south. It is only necessary to travel down the Valley of French 
Creek, from Knauer Town to Kimberton, to recognise the probable truth of this picture. The 
notion of an undulated or folded structure in the gneiss, finds corroboration in the parallel 
arrangement of the hills and valleys, and in the sudden changes in the dip of the strata, where- 
ever we make a transverse section through the region ; but it receives its most positive demon- 
stration when we study the topography and distribution of the gneiss on the western side of the 
county. There, as we have already seen, several long tapering tongues of the Gneiss formation 
project forward towards the W., including between them actual troughs of the Palseozoic rocks, 
a feature not attributable to any other mode of elevation of the gneiss than that of an undu- 
lation of its general floor, in the manner of long anticlinal waves. Some of these waves, no 
doubt, are so closely compressed, or folded, and others are so irregularly dislocated, as to render 
the analysis of them obscure or even impossible, yet the geology of the country clearly estab- 
lishes their presence. 

Faults. — Even in the more central tracts of the district, we are presented with some interest- 
ing evidences of these crust-undulations. I allude now to a succession of parallel dislocated syncli- 
nal axes, running through West Pikeland and West Vincent townships. Though externally the 
presence of these faults with a synclinal dipping of the strata is not recognisable in any exposures 
of the strata, the artificial development of the ground, in a series of excavations for valuable 
deposits of iron ore, has recently enabled me to discover their existence and true structure, and 
to show that all the principal accumulations of ore are seated upon them. These faults are all 
connected with the trough-like or synclinal position of the strata supporting the ores. But the 
most conclusive proof of undulations in the gneiss, and one which accounts for the presence of 
these deposits of iron ore, is the occurrence at almost every dislocation of an insulated patch of 
the Mesozoic red sandstone. The iron ore usually rests in a cleft or deep narrow trough, confined 
between steeply-dipping beds of gneiss, or a wall of granite on the one side, and moderately steep 
south-east dipping strata of the red sandstone, wdthin or behind which no ore is ever found, on 
the other. These strata of red sandstone are invariably highly altered and crystalline, for they 
contain frequently minute crystals of mica, specular iron ore, graphite, and even felspar. Yet, 
in other layers of mottled and half-baked red shale, in close alternation ^^'itll these more altered 
ones, we see proof of their unquestionable identity in composition and origin with the red sand- 
stone formation, from the general southern margin of which, some of them are separated by an 
interval of fovir miles. It seems highly probable that, at the completion of the red sandstone 
deposit, there were several very narrow troughs of it, reposing within some of the deeper valleys 
lying between the hills of the basin of Pickering Creek ; and that at the time of the elevation 
of the formation, or possibly, contemporaneously with the movements which accompanied the 
injection of the mineral veins of the Phoenixville and Perkiomen district, these troughs were 
dislocated longitudinally, and all the superficial red sandstone w^ashed away, except those narrow 



IRON ORES. 



87 



strips wliicli were caught or nipped within the broken synclinals between the sides of the faults. 
In this manner we may readily account for the existence of these outlying narrow belts of the 
red sandstone, and for the presence of the deep and rich deposits of hematitic iron ore which 
they contain, and which have evidently been derived by percolation from thin strata, by the 
lono--continued tricklino- of the surface-waters in the lines of fracture. Above the Friends' 
IVIeeting-House, a bed of a singular, hard, hornblendic rock crosses the road, appearing also on 
the road leading from the Yellow Springs to the Eed Lion, two miles above the latter place- 
Pipe-clay occurs in Uwchlan Township, in considerable abundance. Graphite is said to occur- 
in West Nantmeal, disseminated through blue quartz, l)ut none was met with. 

IRON ORES OF THE GNEISS. 

Brown Iron Ore, or Hematite, of the Basin of Pickering Creek near the Yellow Spring,^, 
and the Geological Conditions under ivhich it occurs. — Allusion has already been made to the 
deposits of brown hematitic iron ore in West Pikeland and West Vincent townships in 
the Valley of Pickering Creek ; and it was stated that these, with very few exceptions, are in 
close relation with lines of sudden fracture, or parallel longitudinal faults, ranging along the 
lesser valleys of the district ; it was intimated, also, that these dislocations are only so many 
ruptured synclinal troughs, enclosing narrow belts or outcrops of a material which, by all 
lithological analogy, can only be referred to the Middle Secondary red sandstone, altered more 
or less by some igneous metamorphic agency. I shall now offer to the reader some sketches 
of the three or four principal deposits in the neighbourhood of the Yellow Springs, which have 
been developed by mining, and which serve best to disclose the law which seems to regulate 
the distribution of the ore. Commencing with the most north-eastern principal excavation, 
the first which we meet with is one about a mile and a half N.E. of the Yellow Springs on the 
new road to Kimberton, and on land owned by Mr Lewis. 

Lewis's Ore Bank. — This deposit, of which a considerable quantity of good brown hematite 
is now sent to the Ironworks at Phoenixville, rests in a triantrular cleft or narrow trouo-h 
between steeply-dipping gneiss rock on its S.E., and more gently -pitching altered red sandstone 
and shale, declining south-eastward at an angle of 45° on its N.W. White felspathic granite 
occurs near the southern waU of the fissure. The ore itself is confined almost entirely to the 
loose earthy matter occupying this long open trench, very little of it penetrating the adjoining 
rocks. It is a somewhat sandy variety of ordinary brown iron ore. The excavations here, all 
of them open to the day, extend to a depth of between 30 and 50 feet below the level of the 
soil, and their longitudinal distribution is N.E. and S.W., for this is the direction of the trough 
which includes the ore. Some of the more altered, or highly crystalline fragments of the red 
sandstone, contain numerous flat plates or spangles of plumbago, besides crystals of specular 
oxide of iron. The more argillaceous layers of this outlying fragment of the red sandstone 
formation, exhibit a less degree of alteration from the normal aspect of the red shale, though 
they are generally mottled and much discoloured, and even sub-crystalline, and speckled with 
minute centres of segregation. The topographical relations of this gulf between the strata, con- 
taining ore, are just such, it should be observed, as we might look for upon the assumption of a 
synclinal flexure in the strata, with or without a disruption. In other words, the line of the 



88 



MIDDLE ZONE OF GNEISS. 



fault or fissure is centrally along tlie bed of a narrow but quite extended valley ; and it should 
be mentioned, that such are the external conditions under which we find nearly all the larger 
deposits of iron ore in this district. It may not be amiss to state here, that it is in this same 
line of valley that w^e find another collection of hematitic ore a little more than one mile to the 
N.W. of the Yellow Springs ; and it is an interesting fact that the bed of ore, a little S. of 
Kimberton, lies almost exactly in the same fine. I would not, however, here wish to intimate, 
that either of these two last-mentioned deposits can be recognised as occupying the line of fault 
in the strata in which we recognise the loose ore. It seems probable, indeed, that the western 
deposit is not connected with any synclinal trough in the rocks, but is the result of an extensive 
decomposition of very ferruginous beds of the gneiss. Possibly, however, this part of the vaUey, 
like that at the Lewis Mine, may once have been overspread by a nai-row thin capping of fer- 
ruginous red shale and red sandstone. 

Fegeleys Ore Beds, near Yellow Spinngs. — About half a mile N.E. of the Yellow Springs, 
two rather extensive excavations have developed a large deposit of the brown iron ore ; one of 
which is known as Fegeley's Mine. They occur in the bed of a little narrow valley which runs 
just N. or back of the high hill, at the S. base of which the Yellow Springs are situated, and 
which is separated from the valley containing the Lewis Ore Bed by a narrow belt of gneissic 
hills. Both of the ore pits at Fegeley's, lie within one long trough or trench in the strata. This 
is embraced by steeply-dipping and twisted beds of micaceous gneiss on one side, and by a narrow 
outcrop of altered red sandstone on the opposite or N.W. side. This sandstone dips south-east- 
ward, at an average inclination of about 40°, to abut apparently against the wall of gneiss rock, 
making with it a long, deep, narrow trough or trench, 100 feet or less in width at the surface, 
and in many places perhaps as deep. Irregular injections of half-decomposed felspathic granite 
penetrate the gneiss of the southern wall of the basin. Ore occurs, confusedly mingled in with 
the rotted materials of the gneiss and granite, but the main body of the ore is in loose earth 
resting against the N. sloping wall of red sandstone. The principal excavation at Fegeley's 
Mine is about 200 feet long, 100 feet wide, and 50 feet deep ; but ore is known to exist in 
many places in the bottom of the pit. The irregular bed of ore itself is about 40 feet wide. 

The outcrop of red sandstone which bounds this line of iron ore on the N.W. forms a low 
ridge, not more than 200 yards broad, traceable, at intervals at least, by tlie soil and surface 
fragments for half a mile or more N.E. and S.W. All topographical indications suggest, that 
exploration should be made for ore in the line of prolongation of this ore-deposit of Fegeley's. 

A short distance to the N.E. of Fegeley's chief ore-pit, there is a yet larger one in the next 
field, accompanied by corresponding geological features, and where likewise the ore dips to the 
S.E., reposing against a slanting wall of altered red sandstone. In the bottom of this pit the 
bed of ore has a thickness or width of about 1 2 feet. 

A careful inspection of the ore and all the attendant phenomena disclosed in these excava- 
tions, cannot fail to suggest the notion, that the ferruginous red sandstone is the source of the 
iron ore, and that it has yielded it up by a process of filtration and percolation of the surface 
waters, by w^hich it has been carried down into the cleft between the rocks, and left there to 
concrete. 

The average annual yield of Fegeley's Mine is about 2400 tons. It is conveyed to the 
furnaces at Phoenixville. The mine adjoining Fegeley's, yields yearly about 2000 tons. 



mON ORES. 



89 



OEE-DEPOSITS SOUTH-WEST OF YELLOW SPRINGS. 

Latschaw Mine. — A third line or narrow belt of iron ore occurs to the S.W. of the Yellow 
Springs, commencing probably in the meadows of the Valley of Pickering Creek. S.E. of this 
attractive place of public resort, two principal mines are seated along this line : one about three- 
fourths of a mile S.W. of the Springs, known as the Latschaw Mine ; the other, about three- 
fourths of a mile further S.W., called generally the Steitler Ore Bank, owned by Eeeves, Buck, 
& Co. of Phoenixville. These are seated apparently on one line or fault, which brings in contact 
in a narrow trough, a long narrow outcrop of Middle Secondary red sandstone and steeply- 
dipping beds of Gneiss. Nearly the same geological conditions prevail at both of these mines, 
namely, crushed beds of red shale or sandstone dipping to the S.E., and abutting against nearly 
perpendicular strata of gneiss, with generally an intervening vertical wall of white felspathic 
granite in a more or less decomposed state. 

In the Latschaw Mine, the stratum of red sandstone seems to have been caught in a deep 
fracture in the gneiss, and greatly squeezed and crushed. The iron ore reposes on the slanting 
face of this compressed mass of sandstone and of shale, and is even dispersed or mingled through 
its fragmentary materials along the line of the fault. So crystalline is the red shale and sand- 
stone, and so full of scales of segregated mica and plumbago, that the observer is sometimes 
at a loss to decide, from hand specimens, whether the rock is really an altered sandstone or a 
variety of gneiss. 

The Steitler Ore Bank. — This valuable deposit of iron ore, evidently lying in the same 
great fissure in the gneiss which contains the Latschaw deposit, fills a deep triangular trough 
between beds of crushed red sandstone on the N. side dipping S., and a perpendicular dyke of 
white felspathic granite, which bounds the gneiss and forms the southern wall of the fissure. 
Except in the existence here of a more regular and massive dyke of granite, the geological 
conditions under which the ore occurs are almost identical with those which prevail at the 
Fegeley and Lewis Mines in the Basins N.E. of the Yellow Springs. 

The annexed Sketch represents the relations of the ore, and of the different strata to each 
other. 

The Steitler Ore Bank has been wrought for the past eight years without interruption, yield- 
ing annually from 3000 to .5000 tons. It was first worked some fifty years ago by a Mr Van- 
leer. The ore from this mine is rich, and generally of excellent 
quality. A little black oxide of manganese, and also a little sul- 
phuret of iron, are occasionally found with the ore. Very beautiful 
masses of fibrous haematite, some of them delicately stalactitic, are 
frequently met with in this mine, which contains a more than usual 
abundance of those hollow geodes, which are sometimes called Bomb- 
shell Ore. It is not uncommon in this and other kindred deposits 
to meet with beautifully white plumose mica, enclosed within these 

and other cavities of the ore. The source of such mica, so insulated, is a point of much interest 
in the theory of the origin of crystalline veins and minerals, and every occurrence of this sort 
may furnish food for chemico-geological speculation. 

Jones' Mine, near Yellow Springs. — This small excavation for iron ore is near the Latschaw 

VOL, I. M 





90 MIDDLE ZONE OF GNEISS. 

Mine, but not upon the same line with it, being seated upon another rupture in the strata, about 
one-eighth of a mile S. of that. At this pit there seems to be a line of fault in the strata, filled 
with fragments of gneiss, of intrusive w^hite granite, and of highly-altered crystalline red sand- 
stone. The iron ore, in a crude and sandy state, is interspersed through this confused mass, which 
it serves more or less to cement. On the South side of the trench containing the ore, we meet, as 
usual, with steep strata of gneiss, and on the North side with South-east-dipping beds of a rock 

which, from its highly crystalline condition, and its abounding in mica 
and in specular iron-ore, greatly puzzles the observer to determine whether 
it also is gneiss, or a highly-metamorphosed form of the argillaceous 
^ red sandstone. This mine is not at present deep enough to exhibit the 

geological phenomena in that distinctness under which we witness them 

Fig. 2.— Jones' Mine. d o J. 

at the Steitler and the Fegeley Mines, and some doubt must remain 
whether we have here another outlying narrow belt of the red sandstone or not. Here is a 
little sketch, which is deemed to represent correctly what is actually visible at this opening in 
the strata. 

Iron Ore in Uwchlan Township. — Iron ore occurs on the West Chester and PottsgTove State 
Road, one-fourth of a mile N. of the Little Eagle Tavern in Uwchlan Township. It occurs in 
gneiss, and evidently at a ftxult in the strata, and some of the fragmentary rock adjoining. The 
ore resembles much the altered red sandstone of other ore localities. This ore has not been 
much explored, and the two or three pits here dug are very superficial. On nearly the same 
line or strike, similar iron-ore may be recognised near the Morgantowii Road, on a farm of 
Morgan Hoffman, and a small ore pit has exposed good ore in a field, owned by William Parker, 
nearly in the same line, which coincides almost precisely with the strike of a narrow belt of 
sparry limestone, which ranges through Morgan Hoffman's farm to George Downing's. Whether 
this limestone is a true igneous dyke or vein of carbonate of lime, or a closely-compressed synclinal 
trough of sedimentary limestone metamorphosed by heat, I will not undertake to say. It extends 
about a mile and a half in a straight line. It is an interesting fact, having some bearing perhaps 
upon the question of the origin of the iron ores I have been describing, that several of these deposits 
adjom, if they are not closely connected with, outcrops or outbursts of limestone. This is the 
case at the Lewis Ore Bank, where, it is said, a narrow strip of limestone has been uncovered in 
the excavations for ore. It is likewise true of the locality of Kimberton, w^here a small exposure 
of highly-crystalline sparry limestone, with spangles of plumbago, occurs within 100 or 200 feet 
of the limestone, and we have seen that it obtains also in regard to the ore at William Parker's, 
which is evidently adjacent to the limestone belt of Morgan Hoffman's farm. 



CHAPTEH III. 



NOKTHERN ZONE OF GNEISS, 

OK GNEISSIC ROCKS NORTH OP THE MESOZOIC RED SANDSTONE. 

GNEISSIC ROCKS OF THE SOUTH MOUNTAINS. 

Boundaries. — The South 'Mountains between the Delaware and Schuylkill Rivers, though of 
comparatively humble elevation, constitute part of a great mountain system, which extends 
through New J ersey and New York under the name of Highlands, and through Maryland and 
Virginia under that of the Blue Eidoe. 

Entering Pennsylvania at the Delaware River, they occur as a broad tract of nearly parallel 
but irregularly- connected ridges, ranging in the direction of their length from the N.E. towards 
the S.W., and having an average breadth of from seven to nine miles, until we approach the 
Schuylkill. These ridges rarely possess a height of more than 400 or 500 feet above their 
adjoining or included valleys ; though their bold undulating outlines, and the rugged steepness 
of their slopes, clothed usually with forest, give to their scenery a prevailing mountain character. 
Enclosed among these hills, as m so many basins, lie several soft and fertile little valleys, the soil 
of which reposes on the beds of our Appalachian Auroral limestone. The materials, not only of 
the well-defined ridges, but of the elevated portions of the tract generally, are either rocks 
belonging to massive and thick-bedded varieties of gneiss, or they consist of the Primal white 
sandstone, the lowest in geological position of our older or Palaeozoic secondary strata. To the 
nature of these materials, and to the violence of the uplifting action to which they have been sub- 
jected, we must ascribe the rugged and sterile character of these hills. Owing partly to the greater 
intensity in the quarter next the Delaware of the subterranean disrupting forces, partly to the less 
thickness in this direction of the white sandstone overlying the gneissic strata, these latter are 
here much more extensively developed than they are further Westward towards the Schuylkill. 

Before entering upon a more detailed account of the areas occupied by the several formations 
constituting the range of hills before us, let us trace the general boundaries of the whole belt, 
and show how it is related in geographical and geological position to the other tracts which confine 
it on the N.W. and S.E. We shall then be prepared to delineate hereafter with precision the 
situation of the irregular insulated patches of limestone, sandstone, and other materials embraced 
among these hills. 

Geographical Range of the Rocks of the South ^fountains.— 'Tracing, in the first place, the 
South-eastern limit of the tract, we find it to coincide pretty accurately, along its whole extent 
from the Delaware to the Schuylkill, with the North-western margin of the Mesozoic red shale 
and sandstone rocks, which spread to the S. so extensively through Bucks and Montgomery 
counties, and which here overlap and conceal the group of rocks we are about to describe. 

At the Delaware River, the boundary in question passes close to the little village of Monroe, 



92 



NOKTHERN ZONE OF GNEISS. 



being more exactly marked by a small stream which flows at the base of the hills. Taking a 
course somewhat W. of S., the line runs about three-quarters of a mile N. of Bursonton ; then 
crossing Durham Creek, ranges westward to the vicinity of Opp's Tavern, beyond which it bears 
to the N.W., approaching Leitz's Tavern about two miles S. of Hellertown. From this point 
the line of division between the two classes of rocks ranges in a direction a little S. of W., until 
it meets the South Branch of Saucon, about half a mile N.W. of Cooperstown. Here turning 
rather abruptly, and assuming a nearly South-western course to the head of Hasacock Creek, 
which it pursues for some distance, it sweeps more to the W. and passes out of Lehigh into 
Berks, crossing the line not far from the Northern corner of Montgomery. 

Entering Berks County, the line crosses the Sumanytown Road a short distance to the N.W. 
of Eitz's Inn ; then taking a course about 50° S. of W., and nearly parallel with the Montgomery 
County line, it ranges N. of the northernmost of the two Meeting-Houses in Hereford Township, 
keeping a little S.E. of Mount Pleasant Iron-Mine, and crossing Swamp Creek about a mile 
above the county line. It next ranges through Boyerstown to Rhoads' Mill on Ironstone 
Creek, keeping S. of the road to Kline's Tavern, and curving at the same time AVestward and then 
North-westward, it passes the Manatawny Creek a little below the line of Amity Township. 
From this point the margin of the tract ranges N. of W. to the intersection of the LimekiU 
Creek and the Township Road of Oley and Exeter. Here it turns again South-westward to 
follow a somewhat undulating line to the Schuylkill, crossing in its route Monokesy Creek a 
quarter of a mile S. of Snyder's Mill, then passing near a little church, crossing Ranch Creek, 
and finally curving round the base of the Neversink Hill to the river. 

Along the whole of the line just traced, the Gneissic rocks and the Auroral limestone, where 
this occurs, are overlaid unconformably by the edge of the Middle Secondary red sandstone. In 
several neighbourhoods, however, the precise line of junction of the two sets of rocks is difficult 
to trace, owing to the quantity of soil, gravel, and fragmentary matter lodged near the base of 
the hiUs ; this is the case, for example, between the South Branch of the Saifcon and the Hasa- 
cock. In other places, which will be alluded to hereafter in detail, the overlying rock is not the 
ordinary red shale and sandstone of the middle secondary series, but a coarse, variegated, and 
more or less calcareous Conglomerate, identical in geological situation and in aspect with the 
rock commonly called Potomac Marble. 

The North-western boundary of the belt of hills before us corresponds very nearly with the 
South-eastern edge of the great limestone formation of the Kittatinny Valley. Taken as a 
continuous line, it begins at the Delaware River, about two miles below the to^uTi of Easton. 
From this point it forms a somewhat undulating border, stretching to the W.S.W. to within two 
miles of Maiden Creek, a tributary of the Schuylkill, where it suddenly curves to take a 
direction nearly due S. to Reading. In the earlier part of its range, this line coincides almost 
exactly with the Northern base of the Lehigh Hills, maintaining thus, from the Delaware to 
Allentown, a course parallel to the Southern bank of the Lehigh, from which it nowhere far 
recedes. 

South-westward from the vicinity of Allentown, the edge of the limestone bounding the tract 
may be traced by Emaus, IMillerstown, Metztown, and Walnut-town, to the cm"ve near ]\Iaiden 
Creek already aUuded to, where, sweeping S., it passes Solomon's Temple, and takes thence the 
road leading to Reading. 



GNEISS or THE SOUTH MOUNTAINS. 



93 



Though the line just traced marks the general North-western boundary of the South Moun- 
tains, there occur several small detached hills, lying beyond it to the N.W. The longest and 
most elevated of these is Chestnut Hill,, near Easton. This, which is properly a spur of the 
general chain in New Jersey, consists chiefly of the gneissic rocks. Another small ridge, 
consisting also of gneissic rocks, lies in a bend of Monokesy Creek, about three miles N. of Beth- 
lehem. A third still smaller elevation occupies the bend of the Lehigh immediately E. of Allen- 
town, keeping for some distance the Northern side of the river. 

Millhaugh Hill. — Westward a few miles from Eeading there is an insulated tract of gneiss, 
forming, with the sandstone of Millbaugh Hill, an elevated district, the last of the chain of the 
Highlands. Between the Schuylkill and Cumberland County, this is the only representative of 
the South Mountains of our State. The tract is about nine miles long and two wide, and 
extends from the Cacoosing into Millbaugh Hill. Its structure is displayed in the General 
Section No. V. 

I shall now exhibit in detail the geological composition and structure of this chain of hills, 
following the general plan of description already laid down, and tracing the belt from the N.E. 
towards the S.W. 

Composition and Structure. — The rocks which compose this belt of hills between the Delaware 
and Schuylkill Elvers, appertain to three formations : one group belonging to the Gneissic system, 
another to the Palaeozoic Primal sandstone, and a third to thePalasozoic Auroral limestone. The 
gneiss and the sandstone enter cniefly into the ridges and hills, while the limestone, the upper- 
most of the three, partially occupies the synclinal valleys. As the sandstone and limestone 
formations are members of the great Appalachian Palaeozoic system of strata, the delineations of 
their boundaries and features will be reserved for a future chapter, and my present descriptions 
will relate only to the rocks of the Gneissic or older metamorphic class. 

The gneiss of this Northern Belt difiers considerably, in its features and constitution, from that 
of the southernmost tract already described. It is for the most part a massive rock in thick 
beds, bearing much analogy in appearance to common felspathic granite, except that it is 
distinctly stratified. Its prevailing character is that of a mixture of felspar and quartz, with 
but little mica. Sometimes it is a triple mixture of felspar, quartz, and hornblende, and not 
unfrequently the magnetic oxide of iron is disseminated among these constituents. In certain 
belts of the Highlands in New Jersey, this last-mentioned mineral is so common an ingredient 
that it might almost be termed one of the characteristics of the rock. In this felsj)athic or 
granitoid gneiss there is present very little mica, talc, or chlorite, or any of the laminated 
minerals of this order ; nor does the chain contain any extensive beds of micaceous, talcose, or 
chloritic slates, such as occur in the Southern Belt. In the arrangement of the materials of the 
gneiss there is an obvious tendency to a certain parallelism of the crystals, especially the felspar 
and hornblende, which are frequently of a flattish form, and occupy thin alternating layers in 
the rock; 

This marked difference in the composition of the predominant rock of the two gneissic ranges 
must be ascribed to an original difference in the chemical nature of the strata, from which each of 
these sets of crystalline rocks was formed by metamorphic agencies. Besides the essential want 
of correspondence between the two regions in the gneiss itself, I have stated that this Northern 
range contains little or no talcose slate. This is to be explained by the circumstance that in the 



94 NORTHERN ZONE OF GNEISS. 

Eastern part of tlie South Mountains, and throughout the chain of the Highlands in New Jersey, 
there is a general absence, in the lower portion of the Appalachian series, of those slates which, 
further towards the S.W., adjoin the Primal white sandstone, and which, through igneous action, 
have been metamorphosed into the talcose and chloritic rocks of those districts. 

In its geological structure, the chain of the South Mountains or Highlands, between the Dela- 
ware and the Schuylkill, presents us with a beautiful example of a belt or group of parallel and 
somewhat closely-compressed anticlinal and synclinal flexures. A glance at the three general 
Sections, Nos. H., HI., and IV., and at the local sections of this chain, will suffice to show the 
nature of these bold undulations. It will be seen that from one end of the range to the other, 
the gneiss, and the older Appalachian strata in contact with it, are bent into a series of folded or 
inverted flexures, having, that is to say, the strata in the N. leg of each anticlinal turned over, and 
dipping steeply to the S., or rather to the S.E., in accordance with the law so universal through- 
out our whole Appalachian Chain. Near the Delaware, as shown in both the general and the 
local sections, there are three distinct ridges of the gneiss, separated by two synclinal troughs of 
the Auroral limestone. Here the entire breadth of the chain is about 7-g miles. At the Eastern 
corner of Berks County, where Section III. crosses these hills, their breadth is about six miles. 
Here they consist almost exclusively of the gneissic rocks. But near the Schuylkill, as exhibited 
by our sections, the whole belt is much contracted, consisting chiefly of the spurs of the Netersink 
Mountain, and the ridges are composed almost exclusively of the Primal white sandstone, in an 
altered and much indurated state. We do not advance far eastward from the river, however, 
before the Gneiss crops out on the Southern slope of the spur of Penn's S. Mountain, South of 
the town of Reading. 

MORE DETAILED DESCRIPTION OF THE GNEISS AND ITS MINERALS IN THE 

SOUTH MOUNTAINS. 

At the North-eastern extremity of the chain is the insulated ridge called Chestnut Hill. This, 
which is but the South-western prolongation of Marble Mountain, a spur of the chain lying on 
the Eastern or New Jersey side of the Delaware, commences at the river, and passing immediately 
to the N. of the town of Easton, crosses the Bushkill above Hester's Dam, and then subsiding 
into a long and narrow point, sinks under the limestone near Seip's, about four miles from its 
origin. Its rocks, which are well exposed at the passage of the river round its Eastern end, con- 
sist chiefly of gneiss, its Southern flank alone containing other materials, the more interesting of 
these being a belt of talc-schist, serpentine, and various associated minerals, among which are 
zircon, actynolite, augite, silvery mica, soft woolly asbestos, and fine pseudomorphic crystals of 
serpentine. The gneiss belongs to the massive granitoid variety, so common throughout the 
whole chain. Its strata dip at a steep angle towards the S.S.E., but exhibit in many places 
much contortion, implying the violence of the forces, which have uptilted them. The same dip 
is \dsible in the beds of the talc-slate. The blue limestone of the valley encircles the base of this 
hill on every side, except just at the passage of the river. 

Chestnut Plill presents the mineralogist, at several localities, with beautiful specimens of various 
mineral species, especially of the magnesian class. The Northern part of the ridge exposes, on the 
river at " the Weygatt," high, overhanging clifis of a rock of quartz and felspar, containing veins 



EOCKS OF THE SOUTH MOUNTAINS. 



95 



of epidote. To the S. of this, ranging along the Southern slope of the hill, is seen a band of ser- 
pentine and other magnesian rocks, imbedding a great variety of interesting minerals. Next the 
Delaware, the serpentine is mostly of the yellow sort, containing in places rhomljic carbonate of 
lime, with, indurated asbestos, and also grey carbonate of lime in serpentine. Far up the Southern 
slope of the hill occurs a mass of semi-crystalline greenish-grey augite, including flesh-coloured 
carbonate of lime. Near the serpentine are several varieties of tremolite, some of it in bladed 
crystals, some greenish. A little to the westward, near Wolf's Old Quarry, the serpentine 
abounds with nephrite, some of which is of a beautiful bluish tint, some of a delicate pink hue, 
and containing small shining crystals of tremolite. A little S. of the nephrite, indeed apparently 
intermixed with it, are several varieties of talc, as slaty, greenish, whitish, and a scaly green 
kind. Some of the talc is compact, and is mingled with serpentine, and pervaded with white 
fibrous carbonate of lime. 

To the S. of this locality, there extends another band of coarse quartz and felspar rock, in 
which some of the felspar is reddish. This portion of it contains crystals of tourmaline and 
sphene. A belt of this rock occurs at the edge of the river, where it is overflowed at high water ; 
it contains a quantity of soft asbestos, filling the joints. About one mile to the W. of this point, 
being on the same Southern slope of the hill, and a little W. of the Easton and Wind-Gap road, 
a beautiful silvery mica was formerly found in abundance, but is now nearly exhausted. Near 
this occurs a scaly talc, in which good crystals of zircon have been met with. Close to this spot, 
and near the spring that supplies the town with water, is found a white tabular, crystalline tre- 
molite, some of which is minutely dotted with specks of plumbago ; a variety of greenish, tabular 
tremolite is also here. To the westward of this, in a little cleared meadow, were found specimens 
of a serpentine rock, containing flesh-coloured and light carbonate of lime, and also irregular 
masses of tourmaline in a crystalline serpentine. Here, near an old distillery, augite occurs in 
light-green and earthy-looking crystals, with well-developed terminating faces. Still further 
westward, toward the Gap of the Bushkill, and a little S. of a syenite rock, which ranges through 
the ridge, we find a large band of tremolite rock, in the fragments of which are seen crystals of 
grey tourmaline. West of the Bushkill, on the Eastern sloping face of the hill, w^e meet with a beauti- 
ful dark-green variety of serpentine, some of which has delicate streaks of white, probably carbonate 
of lime and asbestos. This band of rock is in solid beds, some of them several feet thick, and as 
it promises to prove susceptible of a fine polish, it may perhaps become valuable as an ornamental 
stone. It is obviously a stratified rock, overlying regularly the syenitic belt of the ridge, which 
here consists chiefly of sahlite, and dips S.S.E., towards the overlapping limestone of the 
valley. Betw^een the solid beds of dark serpentine, lie thinner beds of a more slaty sort, with 
distinct bands of micaceous rock, dividing the serpentine and marking the plane or angle of 
stratification. 

Though upon crossing these crystalline rocks to the Northern side of the ridge, we find them, 
Jiear the Bushkill, in such close proximity to the limestone as to imply the absence of the generally 
interposed stratum, the Primal white sandstone, yet to the westward of this a slate is seen, having 
the appearance of the slaty member of the Primal series, near which occur asbestoid and talcose 
slates, probably portions of the same low Palaeozoic rock. Higher up the hill the blue limestone 
occurs in place, and adjoining it wq find the gneiss. At the first of the above localities, the limestone 
in contact with the crystalline rocks forms only a narrow tongue or point, running in from the 



96 



NORTHERN ZONE OF GNEISS. 



■westward, between the main ridge of Chestnut Hill, and a smaller spur which rnns out to the Bush- 
kill, a little above the new stone mill. This smaller ridge consists chiefly of serpentine and talcose 
rocks, bounded at a short distance on the N. by the blue limestone. Some of the talc contains 
cubic crystals of sulphuret of iron, and some of it is interspersed with fine green serpentine, in 
which crystals of zircon are said to have been found. 

The true direction of the gneissic belt of Chestnut Hill is a little S. of W. Its more elevated por- 
tion terminates a little W. of the Bushkill, beyond which the rocks are much concealed by diluvium, 
cropping out, however, at Seip's Tavern. The high land represented on the Northampton County 
map as the Western prolongation of the ridge, is not strictly a part of it, but a line of limestone 
knobs, occurring south of the true range. 

Before proceeding to the main belt of the Lehigh Hills, a small insulated ridge, met "with about 
three and a half miles N. of Bethlehem, claims attention. It commences a little W. of the road 
leading from Bethlehem to Nazareth, and follows the South side of the Monokesy Creek, in the form 
of a narrow elliptical hill, crossing the stream, and terminating near the road which leads from 
Bethlehem to Mauch Chunk, a short distance W. of which road its gneissic rocks sink away 
under the limestone of the valley. This ridge, formed of the same rocks as Chestnut Hill, in the 
prolongation of which, moreover, it seems to lie, owes its elevation very probably to one and 
the same uplifting force. 

A third detached ridge, consisting chiefly of gneissic rocks, lies between Allentown and Beth- 
lehem, immediately N. of the Lehigh, and parallel with it. The principal rock in this hill is a 
compound of quartz and felspar, in which, however, are occasional seams of hornblende and 
epidote. Its northern side is strewed with fragments of yellowish white Primal sandstone, the 
strata of which appear in place, dipping gently northward, at the Eastern end of the hill, about a 
mile and a half West of Bethlehem. 

Ridges South of the Lehigh. — The chain of the South Mountains, consisting of nearly parallel, 
though often irregularly-united ridges, will be best described by tracing each belt separately. The 
first groupof ridges extends fromtheDelaware to Saucon Creek, where a long narrowyalley, running 
in a transverse direction entirely across the tract, separates this from the other belts further to 
the S. W. Eestricting our attention, in the first place, to the group of hills E. of the Saucon, they 
naturally divide themselves into three ranges : the northernmost, known as the Lehigh HiUs, com- 
mencing at the Delaware below Easton, and terminating near HeUertown ; the middle one, 
beginning also at the river above Rieglesville, and terminating N. of Cooperstown ; and the 
southernmost, lying S. of Durham Creek, and running from the river to Springtowu. 

The first of these, the Lehigh Hills, bounding for some miles the valley of the Lehigh Eiver 
on the S., and commencing in a loop of the Delaware about two miles below Easton, ranges 
towards the S.S.W., and gradually approaches the Lehigh, until the gneiss rocks show themselves 
on the river-bank, about a mile and a half below the mouth of Saucon Creek. Near the East 
Branch of this stream the chain separates, enclosing small tracts of limestone between its spurs. 
■ The gneissic rocks occupy the margin of the river for only a short distance, the limestone, their 
usual boundary, resuming soon its place on the Southern side. This belt of the gneiss terminates 
near the bridge over Saucon Creek, between Shinersville and Freemansburg, the limestone folding 
round the base of the hill, and extending up the East Branch of Saucon. Between this East 
Branch and the Main Creek lie two other ridges or spurs, nearly in a line with the chain just 



THE LEHIGH HILLS. 



97 



mentioned, the Soutliern one terminating E. of Hellertown, and the other further northward. 
Between them is a narrow limestone valley, which contracts in breadth towards the E., and heads 
near the Little or East Saucon. Though a separate chain of elevated rocks, the Northern belt 
here described is not entirely detached from the middle range already referred to, a tract of 
crystalline rocks lying round the head of the Little Saucon, serving to connect them geologically. 

In the general prolongation of the chain, but disconnected from the previous set of ridges by 
the transverse valley of the Saucon and its South Branch, we have the Metamorphic or gneissic 
rocks extending towards the S.W., through the lower townships of Lehigh and Berks, in a series 
of nearly parallel spurs, almost to the Schuylkill. Li describing the general South-eastern and 
North-western boundaries of the whole chain through Lehigh, we have already given very nearly 
the true limits of these rocks in that county. This part of the belt is separated longitudinally 
for several miles, into two parallel sets of ridges, by the upper part of the valley of the Saucon. 
One of these tracts, lying W. and N. of that creek, commences at the Lehigh, near Bethlehem, 
and ranging S. of Allentown, and past Emaus and Millerstown, passes into Berks, losing there 
its character as a distinct zone of hills ; the other originating W. of the South Branch of Saucon, 
ranges South-westward to the head- waters of Perkiomen Creek, where it merges westward into 
the general belt. On both sides of the county line, dividing Lehigh and Berks, the Gneiss Hills 
compose an unbroken tract having a breadth of about six miles. Passing still further to the 
westward, the general chain expands in width, but becomes subdivided by valleys entering it 
from the S. and W. ; the broad gneissic tract being broken into about five spurs or ranges, and 
the intervals between them occupied by belts of limestone and sandstone, the latter often 
forming hills as elevated as those of the gneiss. The northernmost subdivision of the gneiss, 
starting from the general belt in Rockland Township, terminates about three miles E. of the 
mouth of Maiden Creek, near the head of Dry Pam. It is bounded on the N.AV. by a narrow 
undulating belt of the Primal sandstone, which, from the neighbourhood of Metztown to 
Solomon's Temple, separates the gneiss from the limestone of the Kittatinny Valley. This tract 
of the gneiss is bordered on the S. by a long narrow tongue of the same sandstone, starting off 
from the main mass of that formation E. of Solomon's Temple, and running eastward past 
Pricetown as far as Shiffert's Inn. W. of Penn's Mountain, which consists of the sandstone, 
and S. of the Pricetown range of the same rock, lies another nearly-detached tract of the gneiss, 
bounded on the E. and S.E. in Oley and Exeter townships by the Primal slates and the Auroral 
Limestone. The margin of this large patch of strata is made so excessively irregular, by the 
protrusion into it of the spurs of sandstone, as to render it impossible to describe it intelligibly 
in words. A third spur of the general chain occupies the Southern half of Eockland Township, 
between the two head-streams of Manatawny Creek. A fourth smaller spur projects to the 
S.W., forming the Northern corner of Pike Township. It is bounded by Pine Creek on the N.W., 
and by another parallel stream, also a tributary of the Manatawny, on the S.E. A fifth and 
much larger tract of the crystalline rocks fills the South-eastern part of Pike, the North-western 
two-thirds of Colebrookdale, and the Northern half of Earl townships. It is limited on the N.W. 
and W. by a long, narrow, curving belt of the sandstone, which follows the Eastern side of the 
tributary just mentioned, and then the Main Creek. Its Eastern border passes through Cole- 
brookdale Township, from Perkiomen to Ironstone Creeks, making here a gently-undulating line, 
nearly parallel with the Montgomery County line. This South-eastern edge of the gneiss is 
VOL. I. N 



NOKTHERN ZONE OF GNEISS. 



formed by the margin of the overlapping red sandstone of the Middle Secondary 
period, except at a few points, where small patches of the limestone and white 
sandstone intervene. Between the head of Ironstone Creek and the main Mana- 
tawny, near Spang's Furnace, there extends a small ridge of the Primal white 
sandstone, which separates the Gneiss tract along its southern limit into two 
divisions. A line drawn from a point on Ironstone Creek, about a mile S.W. of 
Boyerstown, westward to the end of this sandstone ridge, will mark with toler- 
able accuracy the general limit of the Gneiss on the S. 

STEATIFICATION OF THE SOUTH MOUNTAINS, AS SEEN IN 
TRANSVERSE LOCAL SECTIONS. 

Section (A.) — Along the Delaivare River W. side {looking S.W.) — The best 
natural exhibition of the structure of the Delaware and Schuylkill division of the 
South Mountains, indeed the only good one, is that along the first-named river 
from Easton to Monroe. Eeserving for a future chapter the longitudinal tracing 
of the synclinal belts of the Palseozoic strata, their positions and features in the 
sections will be noted here, as essential to a clear understanding of the constitu- 
tion of the chain. 

Commencing at the mouth of the Lehigh, we first encounter the Auroral 
limestone of a dark blue colour and ferruginous aspect. Near the Lehigh Bridge 
its strike is irregular, for it dips to S. 20° to 45° W., at an average angle of 25°. 
The rock shows some metamorphism, is massive and free from joints, but displays 
a transverse cleavage dipping 60° to S. 40° E. The S. dip continues for two- 
thirds of a mile below the Lehigh, but is steeper when it changes to a gentle N. 
dip of 20°. Approaching the foot of the Lehigh Hill it becomes more altered and 
slaty, the partings between the beds being covered by a thin micaceous film ; 
here the cleavage planes are more conspicuous than the planes of bedding. It 
is worthy of note that in this locality the strike of the cleavage is. not coincident 
with the strike of the Palseozoic rocks to which it belongs, nor yet with the 
strike of the Gneiss upon which they unconformably repose. The strike of the 
Gneiss in this district varies from N. 50° E. to N. 45° E. ; that of the Palseozoic 
rocks is usually about N. G5° E. But the strike of the cleavage planes of the 
latter, though approximately conformable to that of the beds, is generally more 
E. and W. by several degrees. In the general direction of their dip, the cleavage 
planes observe the usual law, declining steeply to the S.E. 

Quitting the limestone, and crossing a space of 500 feet without exposures, we 
come upon the Primal rocks of the Northern flank of the Lehigh Hills in a highly- 
altered condition ; the first met with are numerous fragments and masses of the 
Primal silicious slates, and the Primal white sandstone, but not in place. From 
beneath these, rise massive beds of a grey quartzose conglomerate, greatly altered 
by igneous agency. Its pebbles, of pea and nut size, are in fused contact with a 
syenite or syenitic gneiss of felsj)ar and augite, the whole rock so altered that 



UNCONFORMITY OF PPJMAL AND GNEISS. 



99 



its sandy paste contains regularly-formed crystalline felspar. It is at once a conglomerate and 
a porphyry. These beds dip 75° to N. 40.° W. 

From below the Primal rocks rises an arch or anticlinal wave of granitoid gneiss with thin 
injections of syenite. On the S.E. side of this anticlinal ridge of gneiss, the Primal sandstones 
and slates again appear all highly altered, some layers of the slates being porphyroidal. Here the 
dip is about 35° to the S.E. Between these two exterior belts of Primal strata flanking the 
ridge, there occurs a narrow compressed trough of the same rocks, involving a synclinal fold 
of the lowest beds of the Auroral limestone. The Lehigh Hill appears, therefore, to contain two 
folded anticlinals. 

Unconformity of the Primal Strata to the Gneiss. — The j)i'ecise angle of dip of the 
underlying Gneiss is not well exposed, but it seems at the N. base of the hill to be steeper than 
that of the Primal conglomerate, implying a movement of the older rock before the deposition of 
the materials of the newer. In other localities, embraced within this line of section, the want 
of parallehsm between the two systems of strata is better displayed. 

Between the Southern foot of the Lehio;h Hill and the Northern base of Bucher's Hill, there 
intervenes a comparatively wide and smooth valley of limestone. This trough rapidly contracts 
and descends south-westward, terminating about two miles from the river ; it is not a simple 
synclinal belt, but contains some two or more anticlinal undulations in the limestone. Between 
the Northern limit of this basin at Eaub's Ferry, and the immediate Southern base of the Lehigh Hill, 
we detect another small trough of the limestone, separated from the main one by a mere narrow 
point or spur of the older crystalline rocks. Along our line of section there are several large 
quarries of the limestone at eligible localities facing the river. One of these displays Eipple 
Mark on a truly superb scale. This quarry is close to Uhlersville. 

The next belt crossed by our section is the tract of Gneiss known as Bucher's Hill. 
Generally the strata are seen to dip to the S.E. at an average angle not exceeding 45° ; they 
are undulated in at least two or three folded flexures, the axis planes of which observe the 
prevailing law, dipping South-eastward. The gneiss here is the prevailing greenish and white 
felspathic variety. 

Between Bucher's Hill, which is the middle ridge, and the Durham Hill, or most Southern of 
the three anticlinal belts, lies another synclinal trough of the Auroral limestone, skirted in one or 
two places by exposures of the Primal sandstone. This belt occupies the valley of Durham 
Creek, as far to the S.W. as Springtown, being on the river, rather more than a mile wide. 
At Durham Furnace the rocks are well exposed. Between the furnace and Durham Creek 
they exhibit a regular anticlinal flexure. This is the locality of the well-known Durham Cave, 
remarkable for the Mammalian Bones which were discovered in it, and which I shall hereafter 
allude to when enumeratino; the fossil remains of our Bone-bearino; Caverns. The cave is 
situated on the North side or steeper flank of the anticlinal arch, which will be found, I think, 
to be the prevailing position of these limestone caverns in the valleys of the Appalachian Chain. 

Durham Hill. — The last belt which the section crosses is that extending between Durham 
Creek and Monroe. The gneiss forming the ridge between the Durham and the Monroe valleys, 
is at the river only about one mile broad ; it is indeed merely a spur of the Musconetcoug 
Mountain sinking down. Its structure is that of a double anticlinal, embracing a very shallow 
synclinal band of Primal strata and Auroral limestone between the two flexures. On the N., 



100 



NORTHERN ZONE OF GNEISS. 



towards Durham Creek, this gneissic belt is flanked by a narrow outcrop of the Primal strata 
succeeded by the limestone. Here we detect one of the most interesting instances of uncon- 
formity of dip between the Palaeozoic and the Gneissic or Hypozoic rocks, anywhere to be met 
with in the South Mountains, or indeed in the Appalachian Chain. The appended little section 
and diagram will illustrate the discordant relation of the two systems, both in dip and strike, 
and serve to bring out distinctly the magnitude of the crust-movement which occurred between 
the periods of deposition of the two sets of strata. 

Fig. 4.- — Unconformable contact of the Primal Rocks and tlie Gneiss. 





At the North base of the hill, the Gneiss, syenitic in its composition, dips 50° to S., 40° E., being 
probably the inverted leg of a folded anticlinal. The Primal rocks lean upon the denuded edges 
of its beds dipping in a nearly opposite direction — namely, 35° to N., 30° W. The whole Primal 
group is here about 100 feet thick, and consists of a lower member, — a dark silicious conglomerate, 
and an upper, composed of alternating beds of altered white sandstone and altered silicious slate. 
Upon these repose the lower beds of the Auroral limestone, conforming in dip and strike with the 
sandstone. On and near the road w^e discern an equally remarkable discordance of strike, that 
of the Gneiss being S. 50° W., while that of the Primal and xiuroral rocks is S. 60° W., or 20° 
away from parallelism. (See Ground Plan.) 

On the South flank, or rather at the South base of the Durham Hills, reclines a narrow outcrop of 
the Auroral limestone, consisting of white magnesian limestone, greenish talcose slate, and blue 
limestone. Abutting abruptly against the latter, we come suddenl}' on the conglomerate, which 
terminates the unconformably overlying Mesozoic red sandstone. This rock is here a true 
puddingstone, being composed of pebbles of all the adjacent older uplifted rocks, — Gneiss, Primal 
sandstone and slate, and Auroral limestone, — imbedded in a paste of red shale. The conglome- 
rate dips 30" to N., 30" W., while the limestones, somewhat twisted, lean to the S. 25° E., at a 
varying angle of from 30° to 60°. This interesting spot marks one point along the Northern 
shore of the broad red sandstone estuary, skirted by a bold range of hills with comparatively deep 
water at their base, where the crust-disturbances which lifted and drained the district shook down 
a large body of fragmentary matter, to be rolled and imbedded by the waters along their base. 

Fig. 5.— Section across the South Mountains between AllentoT\^l and Coopersburg, looking S.W. 





UoraU. ^ Felds. Umisi 



Our next local section designed to exhibit the structure of the chain, extends south-eastward 
from Allentown on the Lehigh, to Cooperstown near the South Branch of the Saucon, a distance of 
about seven miles. The chain as here exhibited is of simpler features than where it is cut by 



SECTIONS ACEOSS SOUTH MOUNTAINS. 



101 



the Delaware, for the southern and central ridges having both expired south-westward, before 
reaching the neighbourhood of our section, the only divisions of the chain presented are, the 
main Northern anticlinal belt in westward prolongation of the Lehigh Hill of the Delaware, 
and a lesser Southern ridge which rises in the forks of the Saucon, and extends south-westward 
towards the Manatawny. 

The first belt of rock included in the section is the Auroral limestone of the valley of the 
Lehigh Creek and River, and the strata dip and undulate almost precisely as they do S. of Easton, 
in a corresponding position at the base of the hills : that is to say, they display an anticlinal 
axis, which a little further eastward, or just S. of the acute bend of the Lehigh, lifts to the surface 
even the Primal sandstone. AVhether the sandstone is directly in contact with the Gneiss, or 
separated from it by a narrow outcrop of the Primal rocks, we are unable, from the absence of 
exposures, to state. 

The general structure of the ridge dividing the valley of the Little Lehigh Creek from that 
of the Saucon, is apparently the same as that of the Lehigh Hill near Easton, or in other words, 
it contains a compound anticlinal, with steep or even inverted north-westerly dips, and more 
moderate south-easterly ones not exceeding 60°. The rock of the Southern slope of this ridge is 
for the most part a hornblendic gneiss, that near the crest is a binary granitoid gneiss of quartz 
and felspar. An obscure slaty cleavage pervades certain portions of the Gneiss, the 23lains 
dipping generally at a steep angle, about 75° towards the S.E. Between the South-eastern base 
of the Lehigh Ridge, and the Northern foot of the subsiding gneissic ridge of the Saucon, there 
spreads a smooth open valley of limestone occupied by the Saucon Creek. Branching southward 
it receives the South Fork of that stream, flowing through another smaller limestone basin. Our 
section-line passes over the Eastern point of the ridge of Gneiss, which separates the main Saucon 
Valley from its southern lateral branch. Tlie Gneiss near the end of the ridge dips at a gentle 
angle towards the S.E., though further to the S.W. this ridge, like that N.W. of the Saucon, is 
anticlinal in its structure. The limestone belt of the main Saucon appears to be undulated ; a 
steep anticlinal axis ranging between the village of Friedensville and the Zinc Mine. This inter- 
esting mine of Calomine, or the silicious oxide of zinc, occurs in a close synclinal fold of the Auroral 
limestone, near the South base of the Gneissic Hills. Passing the spur of Gneiss of the Saucon 
Ridge, we enter a n'arrow belt of South-east-dipping limestone near the South Branch of the Saucon, 
This limestone may be seen almost in contact with the gneiss which supports it, its own beds dipping 
at an angle of 4.5", those of the Gneiss dip 30° to the S.E. ; thus presenting us with another instance 
of unconformity between the two systems of strata. In this case, besides the want of parallelism, 
there is an absence of the whole Primal series, the result either of a dislocation in the strata, or of 
a suspension of sedimentary action in the Primal period at this place, or possibly it has arisen 
from the overlapping of the limestone past the original margin of the sandstone, as both were 
deposited unconformably upon the Gneiss. 

Crossing the South Branch of the Saucon, our section immediately enters the wide area of 
the Mesozoic Red Shale and Sandstone, there terminating in the upper conglomeritic beds of that 
formation, which abut, with a gentle North-westerly dip, against the more steeply South-east- 
dipping beds of the Auroral limestone, under conditions of contact very analogous to those pre- 
sented at Monroe. The red shale formation is well seen half a mile northward from Coopers- 
burg, where its beds show a dip of only about 10°. Here the rock exhibits distinct ripple- 



102 



NORTHERN ZONE OF GNEISS. 



marks. No capping stratum of conglomerate is visible, though the debris of that rock occurs 
near the Hellertown Road ; it has probably been swept away by denuding waters. 



Fia. 6. — Section across the South Mountains, nine miles east of Reading, through Friedensburg, looking S. W. 




This section, like the two already described, commences in the Auroral limestone of the Kitta- 
tinny Valley beyond the North base of the Gneissic ridges of the South Mountains. Passing one 
or two flexures in the limestone, the section crosses a branch of Maiden Creek, and soon meets the 
material of the Primal sandstone, showing a wide, gently-ascending plain to the margin of the 
Gneiss at the foot of the hills. Some portions of the sandstone are pebbly. Entering upon the 
Gneiss, our section crosses an undulating belt of moderately high hills, some five miles in width, 
to the Slate Valley of Friedensburg, which it first touches near Monokesy Creek. This wide belt 
of hills consists in part of Gneiss, in part of Primal White Sandstone ; the latter formation, 
though seldom seen in place, occurring evidently in narrow synclinal basins included between the 
anticlinal undulations of the Gneiss, which, for the most part, occupies the higher ridges. (See 
Fig. 6 — Section, 9 miles E. of Reading.) 

From the foot of the Gneiss Hills, west of the Monokesy, the section traverses a smooth 
gently-undulating plain, the whole way to the Northern margin of the Mesozoic Red Sandstone. 
In the space of about four miles, the first two miles, following the Friedensburg road parallel 
to the section, cross Primal Upper Slate, occupying a broad outcrop before it dips beneath the 
Auroral limestone basin of tlie Manatawny and Monokesy. The remainder of the distance is 
across the Auroral limestone, which exhibits several undulations. The Gneiss of the hills 
traversed by our section is identical in constitution with that of the Lehigh ridge further north- 
eastward. The Primal series, besides containing much white sandstone, embraces beds of a 
coarse conglomerate. 

Cleavage abounds, especially in the Palaeozoic strata crossed by this section, and dips 
almost invariably at a steep angle towards the S.E., obedient to the prevailing law of cleavage- 
dip in the Appalachian Chain. This structure is plainly shown in the limestone S. of Maiden 
Creek, the planes dipping S.E. ; the Gneiss itself in the first hill shows cleavage, dipping very 
steeply to the same quarter, the strata themselves dipping 45° southward. On the Mana- 
tawny the bluish upper Primal slates display cleavage, dipping eastward 45° or 50°, the beds 
dipping 10° to the N.E. : south of the stream the cleavage-dip is still S.E., but at as low an 
angle as 35°. Further on in the limestone, the true dip of which is often obscure, the cleavage- 
dip maintains its usual direction. 

Our section terminates in the red sandstone formation, which contains, as its uppermost 
deposit, a calcareous conglomerate apparently dipping in the very unusual direction of S.W. at 
an angle of 45°. At another locality near the section, its dip is to the W. 30° ; and one and 
a quarter miles from the Yellow Tavern the conglomerate, well exposed on the road, seems to 
dip a little S. of W. as steeply as 50° or 60°. These irregularities in strike and dip imply 
some local disturbance, an inference which is rendered probable from the occurrence of many 
joints intimating partial metamorphism. 



SECTION NEAR EEADING. 



103 



This section, designed to exhibit the structure of the Neversink Hill near its termination at the 
Schuylkill, commences a Kttle below Reading in the Auroral limestone, embraces the excellent 



Fig. 7. — Section across the Neversink Hill of the South Mountain near Reading, looking N.E. 




wJur. M'ig. Ltmest. 



succession of exposures of the rocks afforded by the cuttings along the Eeading Railroad, and 
terminates in the Mesozoic conglomerate at the South-eastern base of the hill about three miles 
below the town. It displays none of the older Metamorphic strata, but only the Primal rocks 
and the Auroral limestone reposing on them. Even in this depressed termination of the chain 
we may detect the presence of the two main anticlinals which undulate the strata of the hills for 
several miles thence to the N.E. Passing from the Auroral limestone of t*he North-western base 
of the hill, dipping with considerable irregularity at a steep angle, towards the first main flexure 
of the Primal White Sandstone which ranges under its central crest, the section crosses a belt of 
undulated and crushed sandy ferruginous slates, highly indurated and much intersected with 
cleavage. These are the Primal upper slates resting upon the Primal sandstone. This latter 
exhibits a double or compound flexure, the steep limb of the arch being towards the N.W., in 
obedience to the more prevailing rule. 

Towards the lower end of the section, exposed in another deep cut of the railroad, another 
normal arch or flexure of the Primal sandstone displays itself, the steeper or North-western side 
dipping perpendicularly, and the gentler South-eastern, at an angle of 60°. For some distance N. 
of this, the Primal White Sandstone, succeeded by the Primal newer slate, highly indurated and 
crushed, exposes a prevailing dip to the N.W. of about 30°. Between the two main anticlinals 
of the mountain there is evidently a deep synclinal trough rising rapidly north-eastward into 
the hill, but at the railroad containing a basin, or rather a cove, of the Auroral limestone, 
evidently much contorted by pressure and metamorphosed by the action of heat. On the 
South-eastern flank of the Southern anticlinal, we detect a narrow outcrop of the same limestone, 
leaning at a steep angle upon the Primal rocks. Throughout this section these Auroral strata 
and the Primal slates and sandstone supporting them, display a very decided amount of meta- 
morphism,and it is interesting to notice that the cleavage — one of the more conspicuous symptoms 
of this change— observes the usual law, and dips steeply to the S.E., or parallel to the average 
direction and angle of the axis planes of the flexures, manifesting at the same time its usual fan- 
like divergence where it is in immediate proximity to the lesser anticlinal and synclinal curves. 

The section illustrates the fine exposure of the Mesozoic Conglomerate, or uppermost stratum 
of the great Red Shale formation visible at the Railroad. It is here more than usually calcareous, 
but contains, besides its numerous pebbles of the Auroral limestone, others referable to all the 
contiguous formations of older date than itself. The conglomerate, dipping about 15° to N. 20° E., 
abuts directly against the steeply -southward-dipping beds of the Auroral limestone. It is 
evident that the conditions attending its origin were precisely identical with those which 
witnessed the production of the same deposit in the region of the Delaware, as already 
explained ; namely, a wild strewing of pebbles, the fragmeuts of the earthquake-shaken hills 
which composed at the time the northern shore of the Mesozoic waters. 



PART 11. 



PALilOZOIC, OR ANCIENT FOSSILIFEROUS STRATA OF PENNSYLVANIA. 



INTRODUCTORY BOOK. 
CHAPTER I. 

A SYNOPSIS OF THE APPALACHIAN PALEOZOIC STRATA OF PENNSYLVANIA IN 

THE ASCENDING ORDER. 

Primal Crystalline Schists (or Azoic Group). — This is a very tliick and widely-diffused 
group of semi-crystalline strata, — indurated clay -slates, talcose, micaceous and liornblendic 
schists, and grey silicious grits, — without visible fossils, but in close physical relation with the 
overlying fossiliferous Primal rocks, and apparently a portion of the Palaeozoic system. 

PRIMAL SERIES. 

Primal Conglomerate. — A heterogeneous conglomerate composed of quartzose, felspathic, 
and other pebbles, imbedded in a silicious or talco-silicious cement. This rock does not appear 
in Pennsylvania, but is largely developed in Virginia and Tennessee, where it has a thickness of 
150 feet. This formation and the preceding seem to lie below the lowest ascertained fossiliferous 
horizon. 

Primal Older Slate. — A sandy slate of a brown and greenish-grey colour, containing much 
felspathic and talcose matter. It has hitherto disclosed no fossils. The thickness of this rock 
has not been ascertained in Pennsylvania, the beds being too much folded. In Virginia it is 
1200 feet thick. 

Primal White Sandstone {Potsdam Sandstone of New York). — A compact, fine-grained 
white and yellowish vitreous sandstone, containing specks of kaolin. This stratum is dis- 
tinguished by a cylindrical stem -like fossil, the Scolythus linearis, which crosses the beds in a 
perpendicular direction. Probable thickness about 300 feet. 

Primal Upper Slate. — A greenish-blue and brownish talco-argillaceous slate, sometimes 
very soft and shaly. Its only fossil a peculiar fucoid. It is probably about 700 feet thick in 
Pennsylvania. 



AURORAL SERIES. 



105 



AUEOEAL SERIES— (BLUE LIMESTONE of the WESTERN STATES). 

Auroral Calcareous Sandstone {Calciferous Sandstone oj^ New Yorh). — A coarse grey 
calcareous sandstone, containing drusy cavities, enclosing crystals of quartz and calcareous spar. 
Within tlie limits of Pennsylvania this occurs chiefly in Northampton, Centre, and Huntingdon 
counties. It is about 60 feet thick at Easton. 

Auroral Magnesian Limestone. {The Chazy and Black River Limestones of New Yorh are 
parts of this formation). — A light-blue and bluish-grey massive limestone, containing generally 
from ten to thirty per cent of carbonate of magnesia. In the south-western portion of Pennsyl- 
vania it contains thick beds of chert. Its thickness is from 2500 to 5500 feet. 



MATINAL SERIES. 

Matinal Argillaceous Limestone {Trenton Limestone of New Yorh). — A dark-blue and 
bluish-grey, soft, argillaceous limestone, alternating near its upper limit with blue calcareous 
shale. This whole formation is very fossiliferous, being characterised by the Chcetetes hjcoj^erdon, 
Leptnsna sericea, Bellerophon hilobata, Isotelus gigas, and many other fossils. In Northampton, 
Miffin, and Centre counties, it is from 300 to 550 feet thick. 

Matinal Black Slate {Utica Slate of New Yorh). — A blackish and dark-blue fissile slate, 
usually very carbonaceous, distinguished by Graptolites, Orhiculce, and other characteristic fossils. 
It appears in Northampton County and in Kishicoquillas Valley. Its thickness is from 300 to 
400 feet. 

Matinal Shales {Hudson River Slates of New York). — Bluish-grey shales and sandy slates, 
containing, especially in their upper portion, many beds of argillaceous sandstone, and some layers 
of dark-grey silicious conglomerate. In the western parts of Berks and Lebanon, the formation 
contains much red and reddish-brown slate, alternating with yellow layers. The middle portion, 
in certain localities, yields a tolerably good roofing-slate. It has many characteristic fossils, 
especially a species of Graptolithus, of Heterocrinus, of Orhicula, of Modiolopsis and other 
Acephala, and of several Trilohites. It contains some species common to it and the Matinal 
argillaceous limestone. Thickness in Centre County, 1200 C?) feet. 



LEVANT series. 

Levant Grey Sandstone {Oneida Conglomerate of Neiv Yorh). — A compact greenish-grey 
massive sandstone, containing, in many places, thick beds of silicious conglomerate. From 250 
to 400 feet thick in many ridges in Centre and Huntingdon counties. 

Levant Eed Sandstone {Division L., or Loivest Memher of the Medina Sandstone of New 
Yorh). — A soft argillaceous red and brown sandstone and red shale. It contains few or no 
fossils. In Centre and Huntino;don it is from 500 to 700 feet thick. 

Levant White Sandstone {apparently Divisions II., LIT, and IV. of the Medina Sandstone 
of New Yorh). — A white or light-grey sandstone, rather fine-grained, very hard and massive, 
alternating at its upper limit with greenish shales, and containing there thin-bedded and mottled- 

VOL. I. 0 



106 



SYNOPSIS OP PALEOZOIC STRATA. 



grey and red sjindstone. These upper beds are often covered witli a network of the impressions 
of large articidated marine phxnts, especially the Ai'tkrophycus Harlani. The freshly fractured 
surfaces of the lower beds are generally dotted with yellow ferruginous specks. In some out- 
crops the whole mass is 450 feet thick. • . 

SUEGENT SERIES. 

I 

SuRGENT Lower Slate {probable equivaleyit of Lower Green Shale of Clinton Group of 
New York). — Olive-coloured and yellowish slates, containing but little calcareous matter, and 
including thin sandy beds. Some of its layers acquire, by exposure, a peculiar claret colour. 
Characterised by the little branching fucoid Buthotrephis gracilis, and other fossils. This 
formation is in some places 200 feet thick. 

SuRGENT Iron Sandstone. — An alternation of red and ponderous ferruginous sandstone, 
red argillaceous sandstone, and green sandy slate. The red sandstone very usually contains two 
or three thin beds rich enough in iron to be valuable as an iron ore. In the Kittatinny Moun- 
tain, on the Susquehanna, it is 80 feet thick. 

SuRGENT Upper Slate. — A green fissile slate, changed at its outcrop into a buff-coloured, 
and sometimes a claret and brownish, slate. It contains thin layers of argillaceous sandstone, 
and abounds in the small branching fucoid Buthotrephis gracilis. Its thickness frequently 
exceeds 250 feet. 

SuRGENT Lower Ore Shale {part, 'perhaps, of the Upp)er Green Shale of Clinton Group, 
Neio York). — A greenish fissile shale, with thin layers of limestone. This formation sometimes 
contains a band of the red fossiliferous iron ore. It has a thickness near Jack's Mountain, on 
the Juniata, of 7G0 feet. 

SuRGENT Ore Sandstone. — A tough grey calcareous sandstone, with thin partings of shale. 
It is from 10 to 30 feet thick. 

SuRGENT Upper Ore Shale {p>robably on horizon of Upper Green Shale of Clinton Group 
of New York). — This formation consists, in Pennsylvania, of an alternation of bluish and greenish 
shales and fissile slates, with thin beds of argillaceous and sometimes pure limestone, and occa- 
sionally tliin beds of calcareous sandstone. Its lower portion is characterised by the well-known 
red fossiliferous iron ore, in one or more thin layers. It abounds in Beyrichia and other fossils. 
On the Juniata it is 300 feet thick ; in some places even more. 

SuRGENT Red Marl {Clinton Group of New York). — A red, slightly argillaceous shale of 
very uniform composition. It contains scarcely any fossils. Its thickness on the Juniata is in 
some places 350 feet. 

SCALENT SERIES. 

ScALENT Variegated Marls. — An alternation of blue, green, and red marly shales and fossili- 
ferous limestones ; the red shale more abundant towards the bottom. It contains Cytherina 
alta, Avicula alia, and other shells. Thickness on the Juniata, about 400 feet. 

ScALENT Grey Marls {probably this and the Scalent variegated Marls represent the Onon- 
dago Salt Group of New York). — Ashy, greenish blue, and grey calcareous marls and shales, with 



SCALENT SERIES. 



107 



occasional beds of impure argillaceous limestone. It graduates upward into the Cement Eock. 
Thickness on the Juniata, 800 feet. 

ScALENT Limestone {Water Lime Gronj) of New York). A blue flaggy limestone, sometimes 
containing bands of chert. Certain portions have a thinly-bedded, wavy stratification. It is 
frequently highly magnesian, and is extensively employed, especially in New York, for making 
hydraidic cement. This rock contains the Cytherina alta, Tentaculites ornatus, and a few other 
distinctive fossils. Thickness on the Juniata, 250 feet. 

PRE-MEEIDIAN SERIES. 

Pre-meridi AN Limestone {Lower Helde7'berg Limestone of New York). — A diversified calca- 
reous formation, usually of some shade of greyish blue. It is argillaceous and flaggy in its lower 
beds, and shaly towards the middle. It frequently contains layers and nodules of chert, espe- 
cially near its upper limits. It has many characteristic fossils, the Pentameris galeatus, and other 
shells, with corals. The average thickness of this rock is between 50 and 100 feet. 

MERIDIAN SERIES. 

Meridian Slate. — A dark ash-coloured and blackish slate, passing upwards into a dark ashy 
grey sandy calcareous rock. It has its greatest thickness on the Upper Juniata, near Franks- 
town, where it is 1 70 feet. 

Meridian Sandstone {Orishany Sandstone of Neiv Yo7'Ic). — A coarse, yellowish, calcareous 
sandstone, graduating near its upper limit into a fine-grained quartzose conglomerate, and 
becoming in its lower beds a coarse arenaceous limestone, characterised by the Atrypa elongata, 
Spirifer arenosus, and other remarkable large Brachiopodous shells. Its greatest thickness on 
the Juniata is about 150 feet. 

POST-MERIDIAN SERIES. 

Post-meridian Grits {Canda-Galli and Schoharie Grits of Neiv York). — A formation contain- 
ing two members hitherto only met with in a limited district in New York. The lower member 
is a dark-greenish argillaceous rock, recognisable by a peculiar plant, resembling somewhat a 
cock's tail. The upper member is a more calcareous grit. This formation is largely developed 
in New Jersey, north-east of the Delaware Water-Gap, where it has a thickness of 300 feet. 

Post-meridian Limestone {Ujyj^er Heldei^herg or Corniferous Limestone of New York, part 
of CUj^' Limestone of Western States). — In North-Eastern Pennsylvania, New Jersey, and New 
York, a blue, and in some portions a sparry limestone, including bands and nodules of chert. 
In Upper Canada and the Western States it is light-grey and straw-coloured, and sometimes 
oolitic, stin retaining the chert. Among its many fossils are numerous large corals, as Favo- 
sites Gothlandica, Favistella, &c., and characteristic shells, as the Pleurorhynchiis trigonalis. Its 
thickness east of the Delaware Water-Gap is about 80 feet. 

cadent series. 

Cadent Lower Black Slate {Marcellus Slate of New York). — A black and highly bitumin- 



108 



SYNOPSIS OF PALEOZOIC STRATA. 



ous slate, graduating upwards into a dark-blue argillaceous shale. In some districts these are 
overlaid by greenish-grey sandy shales. In Pennsylvania, Virginia, and Tennessee, a thin argil- 
laceous limestone generally occurs near the bottom of the black slate. The fossils, Avith few 
exceptions, are of diminutive size, most of them identical with those of the Cadent upper black 
slate. Thickness in Huntingdon, 250 feet. 

Cadent Shales {Ilamilton Group of New York). — Bluish-grey, brownish, and olive-coloured 
argillaceous shales, including in some districts thin beds of dark-grey and brown sandstone. It 
has many fossils, particularly bivalve shells. Thickness in Huntingdon, 600 feet. 

Cadent Upper Black Slate {Genessee Slate of Neio York). — A brownish-black, and in some 
regions bluish-black, very fissile slate, characterised by its small and delicate fossils ; many of them, 
as Leptimia setigera, identical with those of the Cadent Lower Black Slate. It is the lowest 
known horizon of Carboniferous plants. Thickness in Huntingdon, 300 feet. 

VERGENT SERIES. 

Vergent Flags {Portage Flags of New York). — A rather fine-grained grey sandstone in thin 
layers, parted by thin alternating bands of shale. It abounds in marine vegetation. Thickness 
in Huntingdon, 1700 feet. 

Vergent Shales {Chemung Group of New York). — A thick mass of grey, blue, and olive- 
coloured shales, and grey and brown sandstones. The sandstones predominate in the upper part, 
where the shales contain many fossils. Thickness in Huntingdon, 3200 feet. 

PONENT SERIES. 

Ponent Red Sandstone {Catskill Group of New York). — In its fullest development this is a 
mass of very thick alternating red shales, and red and grey argillaceous sandstones. It has very 
few organic remains. Among them is the Holoptychius, and one or two other remarkable fossil 
fishes, of genera distinctive of Old Red Sandstone. This formation has its maximum thickness in 
its south-eastern outcrops, where it measures more than 5000 feet. 

VESPERTINE SERIES. 

Vespertine Conglomerate and Sandstone. — White, grey, and yellowish sandstone, alter- 
nating with coarse silicious conglomerates, and dark-blue and olive-coloured slates. It frequently 
contains beds of black carbonaceous slate, with one or more thin seams of coal. The only organic 
remains are fragments of coal plants ; some of these are specifically, and even generically, difierent 
from those of the Serai coal series. It has its greatest thickness near the Susquehanna, where it 
measures 26G0 feet. 

UMBRAL SERIES, or CAEBONIFEROUS SHALES and LIMESTONES. 

Umbral Red Shales and Limestone. — In Pennsylvania this series consists almost entirely 
of soft red shales and argillaceous red sandstones, gradually becoming, in Virginia and Tennessee, 
a triple mass, the lowest member of which is a mass of buS", greenish, and red shales, "with sand- 



UMBRAL SERIES. 



109 



stones ; the middle a thick body of light-blue limestone, often oolitic ; and the upper, blue, olive, 
and red calcareous shales, embracing massive strata of grey and brownish sandstones. The 
limestone is the principal rock in the Western States. When it is a red shale it is without fossils, 
but as a limestone it is full of organic remains. The maximum thickness of the united Eed 
Umbral Shale, south of the Southern Anthracite Basin, is 3000 feet. 

SERAL SERIES, or COAL STRATA. 

Seral Conglomerate (or Lowest Division of the Coal-Measures). — A grey and whitish quartz- 
ose conglomerate, in massive beds alternating with grey sandstones. It frequently contains one 
or more thin seams of coal. It is thickest in the Sharp Mountain, where it measures 1100 feet. 

Lower Productive Coal-Measures ; Lower Barren Coal-Shales ; Upper Productive 
Coal-Measures ; Upper Barren Coal-Shales. — An exceedingly diversified group, consisting 
of these four subordinate formations. It comprises argillaceous and silicious sandstones, silicious 
conglomerates, shales of almost every colour and texture, and limestones both pure and argilla- 
ceous ; all of these alternating with coal-slates and fire-clays, and numerous seams of coal. The 
organic remains are many species of terrestrial plants distinctive of the true Coal period; likewise 
marine shells, corals, and fishes. 



» 



CHAPTEH II. 

SUBDIVISIONS OF THE PALEOZOIC EEGION, AND BEIEF SKETCH OF THEIK 

STRUCTUEAL FEATUEES. 

In describing the extensive and complicated region of the Palaeozoic rocks of Pennsylvania, 
embracing nearly the entire State, it will be essential, for the sake of clearness, to subdivide the 
whole area into a number of subordinate districts, having natural boundaries, and to observe a 
definite order in the investigation of their details. I propose, therefore, to portion off the region 
into the following tracts : — 

The Divisions of the Palaeozoic region are, — 

First, The South-Eastern District. — This embraces all the tracts of Palaeozoic rocks in the 
south-eastern counties, including those of the South Mountain. 

Second, The Kittatinny Valley District. — The long regular belt of the Kittatinny or Great 
Appalachian Valley. 

Thii'd, The Orwigshurg and Stroudshurg District. — This is the long and narrow zone of 
strata between the southern base of the Kittatinny Mountain and the southern base of the 
Pokono, and its prolongation, the Llahoning or Second Mountain, extending from Carpenter's 
Point to the Susquehanna. 

Fourth, The North-E astern District. — This embraces all the country N.W. of the division 
last mentioned, and N.E. of the Upper Lehigh, and of the North Branch of Susquehanna 
above the Lackawanna, omitting the Coal Basin, and includes the several valleys in Bradford 
and Tioga, which head south-westward between the detached table-lands of the bituminous 
Coal Basins. 

F if til. The Loiver Juniata District. — This complicated belt of ridges and valleys is embraced 
between the Kittatinny Valley on the S.E., and the North Branch of Susquehanna below 
Berwick, Jack's Mountain, and Sideling Hill on the N.W. It includes the valleys east of the Main 
Susquehanna, known as Armstrong's VaUey, Mahantango Valley, and the Valley of Roaring- 
Creek, and that S.E. of the North Branch. 

Sixth, The Upijer Juniata District. — The scarcely less intricate parallel belt included 
between the North Branch, Jack's Mountain, and SideUng Hill on the S.E., and the foot of the 
Alleghany Mountain on the N.W. 

Seventh, The North- Western District. — The tract to the N.W. of the bituminous coal district, 
embracing Crawford and Erie, with parts of Warren and Mercer counties. 

Eighth, The Anthracite Coal Distinct. — This includes not merely the interior of the several 
anthracite basins, but the mountain-belts encircling each, extending generally to the external 
base of the second or outer barrier. 

Ninth, or Bituminous Coal District. — In this tract is embraced the whole of the bituminous 
region, including its insulated northern patches, and all the country to the N.W. of the Alleghany 
Mountain, excepting the portion already assigned to the Fourth and Seventh Districts. 



FIRST DISTRICT. 



Ill 



GENERAL COMPOSITION AND STRUCTURE OF THE SEVERAL DISTRICTS. 

First District. — It has been already fully shown in the first Part of this Work, that the only 
rocks of the Palaeozoic system which appear in the south-eastern district, are those which apper- 
tain to the two lower series, the Primal and Auroral. These rocks appear in six separate belts. 

The First Belt lies south of the Montgomery and Chester Valley ; it is narrow at the Schuyl- 
kill, but expands south-westward, and from the Brandy wine to York counties occupies nearly all 
the space between the valley and the State line. It contains the Primal slates and Auroral lime- 
stone, under conditions of excessive metamorphism. They are closely plicated with inversions, 
especially in the southern half of the belt ; but it is possible to recognise and trace all the 
principal anticlinal and synclinal folds. This tract includes a succession of narrow oblique 
troughs of the Auroral limestone altered into crystalline marble. These are indicated on the Map. 
All the Palaeozoic rocks are much intersected by cleavage planes and joints, and their true dip 
is therefore oftentimes obscure. They are, moreover, so transformed in many instances from 
their original sedimentary type, and resemble so closely the more ancient Gneissic or Hypozoic 
strata, with which they are in contact, that, from the vagueness of the dip, it is impossible to 
define their boundaries with due precision. The Geology of this diversified belt is discussed in 
detail in the text allotted to it ; and for a general notion of it, the reader has but to study the 
Map and Sections, 

The Second Belt is that of the long and narrow Valley of Chester and Montgomery 
counties, where the ridges immediately bounding the valley consist of the Primal slates and 
Primal white sandstone, and the bed of the valley itself of the Auroral magnesian limestone, 
aU greatly altered by difiused igneous action. This belt begins at Trenton, includes only the 
altered Primal rocks as far as Willow Grove ; but thence to Bart Township, Lancaster County, 
it embraces both this series and the limestone. The whole is a narrow synclinal basin, with 
the strata closely folded together, those of both sides of the trough dipping with much regularity 
to the S.S.E. at an angle ranging between 60° and 70°. (See the general and local Sections.) 

The TJiird Belt is a short and slender tract of the Auroral limestone in Buck's County, near 
New Hope, where denuding action has cut through the comparatively shallow Mesozoic red 
sandstone, and exposed this small portion of its Palaeozoic floor. 

The Fourth Belt is the rather complicated one known as the Limestone Valley of Lancaster 
and York counties. Its boundaries are delineated on the Map ; but the altered Primal slates, 
and the still older Gneissic rocks, are in some places so blended in their outcrops, and so similar in 
aspect, as to render their separation somewhat indefinite. This belt exposes the Primal slates. 
Primal white sandstone, and Auroral magnesian limestone, in a number of closely-compressed 
oblique anticlinal and synclinal flexures. (See the general Sections.) The prevailing dip is to 
the S.S.E. ; only on the larger anticlinals do we meet with a dip to the N.N.W. ; and in many 
of these the strata, in descending, steepen, and presently become inverted, dipping Hke the rest 
to the S.S.E. Within the belt there are four conspicuous anticlinal ridges, exposing the Primal 
white sandstone and a portion of the Primal slates : these are. Mine Ridge, Welsh Mountain, 
Chiques Ridge, and the Pigeon Hills. The Auroral limestone of this belt in the fertile region of 
the central part of Lancaster County has been extensively uncovered along its northern border 
by the denudation of the southern side of the shallow overlying red sandstone. Both the 



112 



SUBDIVISION OF PALEOZOIC REGION. 



Primal rocks and the Matinal limestone liave undergone throughout many portions of this whole 
belt a partial metamorphosis, but their alteration has been less excessive than in the more 
southern belt of the Chester County Valley, and the district south of it. 

The Fifth Belt is that of the South Mountains between the Delaware and Schuylkill, includ- 
ing Millbaugh Hill, near Womelsdorf As shown by the Sections and by the Map, the Primal 
and Auroral rocks. along this range occur in a succession of insulated tracts, the Primal sand- 
stone forming, for the most part, the flanks and even crests of many of the hills, sometimes with 
a monoclinal outcrop reposing on the Gneissic rocks, sometimes in swelling anticlinals ; while 
the limestone rests in the included synclinal valleys, and flanks, in some places, the belt on the 
S.E. The anticlinal and synclinal flexures afl'ecting these rocks are, ^^'ith few exceptions, of the 
ohliquc or inverted order, and therefore their prevailing dip is towards the S.E. The strata 
show fewer marks of extreme metamorphosis than those in the preceding belts. 

The Sixth Belt is that of the South Mountains of Cumberland, Adams and Franklin counties. 
It includes only the Primal series, exposing extensively the Primal older slates, especially in the 
south-eastern ridges, for the most part greatly indurated, altered to a sub-crystalline texture, 
and affected by cleavage. The whole of the Primal series is here much thicker, and is more 
extensively expanded over the surface by numerous parallel flexures, than in the eastern South 
Mountains. The sections exhibit clearly the composition and structure of the belt, and show the 
anticlinals and synclinals to be of the oblique and much-compressed class, and the prevailing 
dip to be therefore towards the S.E. 

Second District. — Kittatinny Valley. — The only formations which appear within the limits 
of this naturiilly-defined division of the Palaeozoic region are those of the Auroral and Matinal 
series ; nor are all of these continuously or extensively developed, the principal masses being the 
Auroral mao-nesian limestone and the Matinal newer slate. The Auroral calcareous sandstone 
at the bottom of the series is but seldom seen, and it is only occasionally that we observe at 
the junction of the limestone and slate along the middle of the valley the other two formations, 
the Matinal argillaceous limestone and Matinal black slate. They would seem not to have been 
everywhere deposited so far to the S.E. The Matinal black slate occurs in a very narrow 
outcrop in Northampton and Lehigh, and the Matinal argillaceous limestone is occasionally in 
contact with it in the same region, and appears again in Franklin County. This latter is almost 
the only formation of the whole belt which is obviously fossiliferous, the others being very 
scantily supplied with organic remains. 

In its geological constitution the Kittatinny Valley displays remarkable uniformity. Excepting 
in the south-western part of Franklin County, the whole belt is composed of two great lithological 
zones, the Auroral magnesiau limestone forming its south-eastern side, and the Matinal upper 
slate its north-western. 

In the part of Franklin just referred to, these two formations repeat themselves in several 
short and narrow parallel anticlinal and synclinal outcrops. Through the entire length of the 
valley the strata are folded into a very uniform steep south-eastern dip, in a series of compressed 
flexures. This structure is distinctly illustrated in all the numerous general sections which cross 
the district. It is only hj a careful and minute inspection of the phenomena of the dips that 
the geologist detects in this greatly plicated belt the lines of anticlinal and synclinal flexure. 
These he cannot, however, ultimately fail to recognise, after due practice. They are readily 



SECOND DISTRICT. 



113 



discernible on the Delaware, Schuylkill, and Susquehanna, and on the Cumberland Valley Rail- 
road. In the zone of Matinal slate the flexures are more obscure than in the limestone, in con- 
sequence of the excessive amount of cleavage which, though it affects the limestone, is a more 
prevailing feature of the slate. The almost universal direction of dip in the cleavage planes is 
S.E., or parallel with that of the stratification, or more strictly with the dip of the imaginary 
planes bisecting the anticlinal and synclinal curves or flexures. These cleavage planes in the 
slate, more especially, often efface all marks of the original bedding, and render the detection of 
the few organic remains of the strata very difficult. Along the north-western border of the 
valley the beds of slate have their normal dip, inclining north-westward beneath the sandstones 
of the Kittatinny Mountain ; but along its south-eastern margin, — so general is the inversion of 
the folded limestone, — this formation appears almost everywhere to pass under the Primal rocks 
of the South Mountains ; and were we not familiar with this striking and general fact of the 
close compression and obliquity of the more south-eastern Appalachian flexures, and had we 
not fully established the true infra-position of the Primal to the Auroral rocks, we might imagine 
the latter to be the lower or older group. 

Third District. — Orivigsbunj and Stroiidsburg Valley. — This long and very narrow tract 
consists of the Levant, Surgent,Pre-meridian, Meridian, Post-meridian, Cadent,Vergent, and Ponent 
Rocks, embraced between the south-eastern base of the Kittatinny Mountain and the foot of the 
Pokono and Second Mountain. Between Carpenter's Point and the Walpack Bend of the 
Delaware, we have only the Cadent and higher strata on the Pennsylvania side of the river ; but 
between the Walpack Bend and the Water-Gap, the Post-meridian, Meridian, and Pre-meridian 
Rocks enter the State from New Jersey, and near the Water-Gap the wdiole of the Levant series 
gradually crosses the river. From this point to the Susquehanna, all the formations enumerated 
are included within the belt. 

The structure of the tract is by no means intricate. From Carpenter's Point to the Wal- 
pack Bend, the strata have all a gentle N.W. dip ; but south-westward from that locality, the 
belt contains in most places one principal anticlinal flexure, and in certain localities there are 
lesser ones parallel with it ; but even the main anticlinal does not range the whole length of the 
tract, for that which is the chief axis between the Delaware and the Little Schuylkill, leaves it, 
and passes into the Pottsville Coal-basin, south of Middleport, while another takes a nearly 
corresponding place, entering it from the side of the Kittatinny Mountain, This last dies out 
near the Swatara, and from thence to the Susquehanna the dip is monoclinal and very nearly 
perpendicular, becoming even inverted as we approach the river. The general sections exhibit 
sufficiently the structure of the belt in each different segment of its length. 

Fourth District. — The North-Eastern Counties. — Throughout this extensive district we are 
presented with very little variety, either in the strata, their mode of dip, or the features of the sur- 
face. Between the south-eastern escarpment of the Pokono Mountain, and the northern hue of the 
State, nearly the whole region, if we except the Lackawanna Coal-basin, and tlie mountains 
enclosing this trougli, is a high and much undulated table-land, the south-westward expansion 
of the plateau of the Catskill Mountains, with only a few defined ridges and chains of hills upon 
it. Its strata belong chiefly to the Ponent series, one of the least fossiliferous, least useful, and 
least interesting of all our Appalachian formations. They are spread out in a succession of very 

VOL. I. P 



114. 



SUBDIVISIONS OF PALAEOZOIC REGION. 



flat and wide synclinal and anticlinal waves, as exhibited in Section I., and are therefore approxi- 
mately horizontal. 

This district includes the four anticlinal valleys in Bradford and Tioga, which divide the 
several narrow plateaus in which the bituminous coal-basins terminate towards the N.E. These 
anticlinal belts expose no strata lower in the scale than the Vergent flags and Vergent shales 
which saddle each axis. The other rocks are of the Ponent series, and have their outcrops around 
the borders of each valley. The general sections exhibit the broad undulations of this region. 

Fifth District. — The Mountain-belts of the Lower Juniata. — The rocks exposed in this very 
complicated division of the Appalachian Chain, included between the Kittatinny Mountain on the 
S.E. and Jack's Mountain on the N.W., consist of all the great series of strata from the Auroral 
to the Ponent inclusive. A sufiiciently correct general conception of the structure of the district 
will be derived from a comparison of the Map with the general Sections, and by observing that 
the whole region is made up of three great anticlinal belts, each consisting of a group of several 
lesser undulations, and of four synclinal tracts, likewise compound, but showing fewer flexures. 

The First Anticlinal Belt is that of Perry County. It commences in the Pottsville Coal-field, 
on the Swatara, divides the two western prongs of the basin, and is the anticlinal, separating 
Berry's and Peter's mountains. It lifts, within the limits of our present district, the Ponent and 
Vergent rocks in Powell's and Armstrong's valleys, and crossing the Susquehanna, elevates the 
Cadent rocks in the Half-Fall Mountain. Soon after crossing the Juniata, it ceases to be a nearly 
simple anticlinal belt, and becomes a group of parallel flexures, rapidly widening by the successive 
introduction of new anticlinals. These, as we trace the belt in its gradual sweep south-westward, 
diverge and elevate to the day in the central part of the general tract of Cadent strata, first the 
Pre-meridian, and next the Surgent rocks, showing lower and lower strata as we advance, and 
imparting to each formation a complicated but beautifully w^inding line of outcrop. The more 
south-eastern of these anticlinals pass out early into the Kittatinny Valley, the more north- 
western range through Amberson's Valley, but also enter the Kittatinny near Loudon. 

The First Synclinal Belt is the broad trough of Vergent, Ponent, and Vespertine rocks west of 
the Susquehanna, and embraced between this anticlinal zone and the southern basin of the Kitta- 
tinny Mountain, and called Sherman's Creek Valley. It is the trough of the Dauphin Coal-basin. 

The Second Anticlinal Belt is that of Mahantango Valley, Tuscarora Mountain, and Path Valley. 
This originates as a group of flexures in the north-western part of Broad Mountain, and within 
the district before us lifts to the surface the Ponent, Vergent, and Cadent Rocks in Mahantango, 
and crossing the Susquehanna, brings to view in the great anticlinal of the Tuscarora Mountain, 
the Meridian, Pre-meridian, Surgent, and Levant strata to the Levant White Sandstone. Advanc- 
ing and curving south-westward, the belt develops other parallel anticlinals in Liberty Valley? 
which, passing through the knobs of the Southern Tuscarora Mountain, and the " Locking of the 
Mountains," enter North Horse Valley, and expose the Matinal slates. As these decline others 
rise, and a chief one ranges along Path Valley, bringing up the Auroral limestone. Connected 
with this belt is the anticlinal of M'^Connellstown Cove. 

The Second Synclinal Belt is that of Wildcat and Bufi"alo Creek Valleys. It is the westward 
prolongation of the trough of the Bear Valley Coal-basin. It is a nearly simple synclinal trough, 
containing, west of the Susquehanna, the Vespertine, Ponent, Vergent, and Cadent strata. By 
the coalescing of the first and second anticlinal belts it terminates near the head of Bufialo Creek. 



FIFTH DISTRICT. II.5 



The Third Anticlinal Belt is that of Shamokin Valley, and Shade and Black Log Mountains. 
It is a more simple anticlinal zone than either of the preceding. The flexures which compose it begin 
near the Lehish River, and are traceable between the basins of the Eastern and Middle Coal Remon, 
and through the Catawissa Valley into Roaring Creek Valley in the district before us. In the 
valley of Roaring Creek and Shamokin Creek, the rocks exposed in this zone are the Ponent, 
Vergent, and Cadent. Soon after passing the Susquehanna, the Pre-meridian, and next the 
Surgent and Levant strata, rise to the day upon the expanding anticlinal of the Shade Mountain, 
which, for some distance, is the only flexure of the belt. Approaching the Juniata, as this anti- 
clinal begins to subside, another conspicuous one, that of Blue Ridge, rises, and parallel with it a 
second, still greater one, that of Black Log Valley. The first lifts the Levant White and Red Sand- 
stones into a mountain-ridge with a double crest, while the last-named elevates first the whole 
Levant series, and then the Upper Matinal Rocks in the anticlinal valley of Black Log. This latter 
grand wave upon the crust continues further south than that of Blue Ridge, and dies away soon 
after entering Fulton County, the whole belt there terminating by the closing over of the 
Ponent strata. The anticlinal of Pigeon Cove, at the Maryland line, may be referred to this belt, 
or the second, indiscriminately. 

The Third Synclinal Belt is the long and regularly-curving valley bounded by the second 
and the last-described anticlinal belts. Where it is crossed by the West Mahantango and 
Cocolamus creeks, it is a broad valley of the Vergent and Cadent rocks ; but approaching the 
Juniata, anticlinal undulations elevate the Surgent and Scalent marls and shales, and the zone of 
Vergent and Cadent strata is contracted to the narrow central valley of Tuscarora Creek. The 
belt continues through the little Aughwick Valley of the same narrow dimensions. To this 
s}Ticlinal zone we may refer the trough of Scrub Ridge, in Fulton County. 

The Fourth Synclinal Belt is embraced between the third anticlinal and the foot of Jack's 
Mountain, Montour's Ridge, and Sideling Hill, the north-western limits of the district. This long 
and narrow trough in the strata is traceable from the knob of Catawissa Mountain, as a hilly 
zone of the Ponent rocks following the North Branch, and extending westward towards New 
Berlin. Curving with an ample sweep more and more to the south, the valley, now confined between 
Jack's Mountain, Shade Mountain, and Blue Ridge, includes a series of small anticlinals, which 
lift the Surgent rocks, so that this part of the belt exposes a chain of several parallel outcrops of 
the Vergent, Cadent, Pre-meridian, Surgent, and Levant strata, as far to the S.W. as the Great 
Bend of the Juniata. Beyond this point the belt is of simpler structure, the minor anticlinals 
subside, and the trough contains little else than the Vergent and Cadent rocks to the termina- 
tion of Jack's Mountain. From this latter locality to the southern line of the State, this zone 
becomes monoclinal along the foot of Sideling Hill, showing the Vergent and Ponent rocks dip- 
ping gently westward, first from the Jack's Mountain anticlinal, and then from that of Pigeon Cove. 

In relation to the character of the flexures in this diversified Fifth District, very few words of 
general description will suffice. Nearly all the undulations, both the greater and the lesser ones, 
are bold curves of the normal type, that is to say, have their north-w^estern sides steeper than 
their south-eastern, but not inverted, as in the district of the Kittatinny Valley, nearer the source 
of the pulsations of the crust which caused the flexures. The special features of each zone Avill 
be found distinctly delineated in the numerous general and local sections which cross the whole 
district ; and their geology will be treated of in detail in future chapters. 



116 



SUBDIVISIONS OF PALAEOZOIC REGION. 



Sixth District. — The Mountain Belts of the Upper Juniata and West Branch of the Susque- 
hanna. — In the complicated division of the Palaeozoic region, to which we next proceed, we have 
repeated and extensive outcrops of all the strata from the top of the Ponent to tlie bottom of 
the Auroral series. The general sections from IV. to IX., inclusive, cross the district, and, if 
studied in connection with the Map, will much assist the reader in comprehending the following 
outline. Looking at the structure of the whole district, we perceive it to consist of six natural 
lesser belts or tracts, but not disposed in an order as regular and parallel as those of the district 
just described. 

The First Belt is embraced between the southern part of Montour's Ridge and the base of the 
Alleghany Mountain, and extends lengthwise from east of Harvey's Creek to the western ends 
of Buffalo, AVhitedeer, and "Whitedeer Hole valleys. The rocks comprised within the tract are 
those of the Levant, Surgent, Pre-meridian, Cadent, Vergeut, and Ponent series. On the S.E. the 
interesting anticlinal zone of Montour's Ridge shows all the Surgent and Upper Levant strata. 
North of it runs the long synclinal of the Vergeut and Ponent rocks, investing the western end of 
the Wyoming Coal-basin ; and north of this again there is a long anticlinal tract, crossing the 
upper waters of Harvey's and Fishing creeks, and elevating the same series. In the central 
portion between Montour's Ridge and the end of the Bald Eagle Mountain, the Sm-gent and 
Pre-meridian rocks appear in the region around Milton, with a belt of the Cadent and Vergent 
both north and south of them. West of the Susquehanna this belt is limited by a succession of 
symmetrical anticlinal mountain-spurs, the terminations of as many great anticlinal waves, which 
there lift in gentler undulations the Middle and Upper Levant, Surgent, and Pre-meridian strata 
through the Cadent and Vergent, and impart to the Surgent a very winding line of outcrop, fold- 
ing this series round the points of the mountains and into the coves, or intervening synclinal 
valleys. 

The Second Belt is the well-characterised region embraced between Jack's Mountain and the 
Bald Eagle Mountain. It includes a very remarkable group of grand anticlinal flexures, the top 
of each principal wave forming a long and narrow fertile valley of the Auroral limestones and 
Matinal slates, divided by bold synclinal mountain-ridges of the massive Levant sandstone. 
The larger valleys are Kisliicoquillas, Penn's, Brush, Sugar, and Nittany valleys. These close at 
one or both ends by the gradual coalescing of their mountain-barriers, brought together by the 
declension of the crests of the anticlinal waves. Ten long symmetrical mountain-spurs of the 
Levant white sandstone, curiously arranged in echelon, form the eastern termination of this 
belt. Its western end is near the Juniata, in the two anticlinals of Jack's Mountain and Bald 
Eagle Mountain, not far from Hollidaysburg. 

The Third Belt is an interesting synclinal zone nearly in the prolongation of the former, 
commencing on the N.E. between the two southern terminating anticlinals, and having Tussey 
Mountain for its north-western boundary, and Stone Mountain and the base of Sideling Hill 
for its south-eastern. In this deep and broad trough in the strata, which consists in the main 
of but one ample synclinal basin, with a few lesser undulations, there are contained the whole of 
the Palaeozoic strata of the State, from the Levant sandstones to the Coal strata inclusive, 
excepting only the Post-meridian series, universally absent to the S.W. of the Delaware River. 
In the limited Coal-basin of Broad Top Mountain, we have an outlying patch of bituminous 
coal-measures, denoting not only the depth of this great synclinal wave, but in its remoteness 



SIXTH DISTRICT. 



117 



from the main coal region ^Y. of the Alleghany Mountain, the enormous extent of the denuda- 
tion which the intervening anticlinal belt of country has experienced. 

The Fourth Belt is the narrow anticlinal zone in Huntingdon and Bedford, bounded on the 
east by the eastern base of Tussey Mountain, and on the west by the north-western foot of 
Duunino-'s and Wills' Creek mountains. This tract embraces a chain of fertile anticlinal valleys 
of the Auroral limestone, namely, Morrison's Cove, Friends' Cove, Bean's Cove, and Milliken's 
Cove ; the three first forming the back of a great anticlinal wave, or perhaps more strictly of a group 
of waves. In the central parts of Morrison's Cove, as in the corresponding parts of the Kittatinny 
Valley, the crest of the anticlinal wave exposes the very lowest sandy strata of the Auroral 
series, the equivalents of the Auroral calcareous sandstone (Calciferous Sandstone of New York). 
On the other hand, rocks as high in the scale as the Meridian sandstone rest in the synclinal 
trouffh between Evit's and Wills' Mountain. 

The Fifth Belt is the very long and narrow and continuous valley enclosed between the 
Bald Eagle, Dunning's, and AVills' mountains, on the S.E., and the escarpment of the Alleghany 
Mountain on the N.W. This zone possesses, except where a few local undulations occur, a veiy 
regular monoclinal structure, its strata dipping towards the N.W., at an angle which grows pro- 
gressively less as we advance in that du-ection and ascend in the general series. Its rocks, com- 
mencing with those on the north-western flank of the Bald Eagle range, and terminating near 
the summit of the escarpment of the Alleghany, appertain to the Surgent, Pre-meridian, Meridian, 
Cadent, Vergent, and Ponent formations. Only in the western side of Bedford County are the 
simple monoclinal features of this long valley locally interrupted by the introduction of two or 
three small anticlinal tracts. Throughout the extensive and varied Sixth District, the anticlinal 
and synclinal flexures of the strata are of great length and striking parallelism, and in many 
quarters so singularly regular, as to suggest irresistibly their analogy to a group of stupendous 
waves or billows in a flexible crust. It will be seen by a glance at the sections which illustrate 
this district, that the flexures are, with scarcely an exception, of the normal order, but have, like 
those of the Fifth District, a large arc of curvature, and therefore a prevailing steepness in their 
dips. In a few instances, a longitudinal dislocation of the strata is discernible along the crest, 
or on the north side of the anticlinal waves ; and usually in such cases there is a sudden change 
in the dip, with a loss of regularity in the form of the anticlinals. 

Seventh District. — The Country N.W. of the Bituminous Coal Region. — This division of the 
Palaeozoic region of the State is, as the Map shows, of an irregular, triangular form, being but a 
portion of an extensive natural geological belt, which ranges from southern New York into 
north-eastern Ohio. In stratification and structure, it is by far the simplest portion of the State. 
The only formations which underlie it are the Vergent shales and the Vespertine sandstones, for 
it is an interesting fact that both the Ponent red sandstones and shales, and the Umbral red 
shale, are entirely thinned away before they reach this north-western outcrop of the general basin,, 
enormous as their thickness is in the south-eastern valleys of the Appalachian Chain. 

By the general section (VIII.) it will be seen that across this whole tract the strata exhibit, with 
little or no variation, an extremely gentle dip towards the S.E., passing finally under the Bitu- 
minous Coal Region. From the north-western outcrop of the Lower Coal Rocks, the surface 
gradually slopes north-westward to Lake Erie, descending about 1000 feet. 

Eighth District, — The Anthracite Coal Region. — This is a division of the Appalachian Chain, 



118 



SUBDIVISIONS OF PALAEOZOIC REGION. 



of great apparent complexity of structure, but of remarkable and beautiful symmetry when 
understood. I include in it not only the Coal strata or Serai series, but the Umbral and 
Vespertine formations also, and therefore its curiously inflected boundary will be traced by fol- 
lowing the outer base of each external or second mountain encompassing the Coal-basins and 
valleys of Umbral red shale. In the aggregate, it may be viewed as a broad synclinal tract 
enclosed between the anticlinals of the Kittatinny Valley on the south, and the wide anticlinal 
at the foot of the Alleghany Mountain on the north ; but regarded more in detail, w^e find it 
composed of an extensive succession of moderately steep anticlinal and synclinal flexures or 
waves arranged in several groups or belts. 

The First Belt is that of the Pottsville or southern coal-basin. This is a long synclinal zone 
beginning E. of the Lehigh in the Kettle Mountain, and terminating W. of the Susquehanna 
in the two troughs of the Cove and Buff"alo mountains. This synclinal belt forks into two at 
the knob of Berry's Mountain, where a great anticlinal flexure elevates lower rocks. In the 
interior of this great trough, or the part occupied by the coal strata, there are several subordinate 
undulations of the strata producing important local effects in the distribution of the coal-beds, 
but unconnected with any very conspicuous features of the surface. The Coal-basin itself reposes 
in the middle of the general synclinal zone of the Umbral red shale, and Vespertine conglomerate. 
It begins at the Lehigh, gradually widens to a breadth of four miles at PottsviUe, and at Good 
Spring Creek divides into the two basins of Dauphin and Bear Valley. A more detailed descrip- 
tion will be given in the chapters on the Anthracite Coal strata. 

The Second Belt is a shorter parallel anticlinal tract extending from the Lehigh westward, 
next north of the Pottsville Basin. It comprehends, first, the Nesquihouing Broad-Mountain, 
composed of Vespertine conglomerate ; next, the Locust Valley of Umbral red shale ; and, lastly, 
Broad-Mountain, a table-land consisting of the Serai conglomerate, with a few subordinate narrow 
basins of the Coal-measures. This belt ends westward in the concave sweep of the Mahantango 
Mountain. Broad-Mountain is an elevated plateau, including several lesser anticlinals, which 
pass out into the low valleys of the Umbral red shale, both eastward and westward, by a series 
of loops which separate its synclinal mountain-spurs. The structure of the Xesquihoning 
Mountain is that of a wide, flat, regular anticlinal w^ave, w ith a number of insignificant gentle 
undulations on its summit and northern flank. 

The Third Belt is the important synclinal tract or basin north of Broad-Mountain, which con- 
tains the rich coal-fields of Mahanoy and Shamokin, or the Western Middle Coal-basins. It com- 
mences in the Head Mountain, and terminates westward at the Susquehanna, in the spiclinal 
knob of Mahanoy Mountain. The inner trough, or that of the Coal strata, comprehends several 
lesser basins divided by well-defined anticlinal ridges. 

The Fourth Belt is the broad table-land including the Eastern Middle Coal-hasins. It lies 
between the anticlinal belt of Nesquihoning Mountain on the S., and that of the Wapwallopen 
and North Branch on the N., and extends from near the Lehigh westward, to the western foot 
of the Catawissa Mountain. Its central plateau of the Serai conglomerate comprises five con- 
tinuous and well-marked anticlinal flexures of gentle curvature and dip, forming six smaU and 
shallow troughs of the Coal-measures. The terminations of some of these minor basins are discern- 
ible in the flat mountain-spurs, which protrude eastward and westward from the general plateau. 



EIGHTH DISTRICT. 



119 



The Fifth Belt is that of the beautiful and well-defined Wyoming Coal-basin. As all the other 
belts are severally in contact with each other, so is this one linked to the last described by the 
high table-land of the Vespertine conglomerate between the sources of the Lehigh and Wapwal- 
lopeu. This belt is a very regular synclinal trough, tapering to a point at each end, and sweeping 
with a bold crescent curve, convex towards the S.E. The Coal-measures, as in all the other 
synclinal tracts, are encompassed by a double mountain-crest, the interior consisting of the Serai 
conglomerate, the exterior of the Vespertine sandstone. Within the Coal-basin there are several 
secondary undulations imparting no prominent features to the tract, but afiecting materially the 
local outcropping of the coal-beds. The belt, including the Vespertine strata, originates a few 
miles N. of Carbondale, and gradually curving south-westward and westward, terminates in a 
synclinal mountain-ridge at Fishing Creek. 

A general survey of the relative positions of these several belts of the Anthracite districts, as 
they are depicted on the Map, discloses a curious oblique arrangement. Each more northern 
zone is situated further east than its neighbour. In other words, all the principal anticlinal and 
synclinal flexures of the region are grouped in echelon. 

By consulting the general sections which cross the district, it will be seen that only in the 
first, or Southern Coal-basin, do the flexures approximate to the folded or inverted type. Advancing 
northward, the undulations take on the normal form, and decline progressively in curvature or 
steepness as we proceed. In the Western Middle Coal-basin the strata dip at a moderately high 
angle ; while in the more northern tracts of the Eastern Middle, and the Northern or Wyoming 
belts, they undulate much more gently. This striking gradation is but one instance, among 
many, of conformity to a law which is very general throughout the entire Appalachian Chain, 
namely, that the undulations of the strata open out and decline in steepness as we recede from 
the quarter of maximum disturbance or rupture of the crust, precisely as we see occur in the more 
advanced waves of a broad group of billows suddenly generated upon the surface of a fluid by 
some local force. 

Ninth District. — The Bituminous Coal Region.— \n its composition and structure, this last, 
and much the largest, of all the divisions of the general Paloeozoic region of the State, is extremely 
simple. It comprises only the Vespertine, Umbral, and Serai series, the former in very narrow lines 
of outcrop, bordering and dividing some of the coal-basins, except in the north-eastern part of the 
district, where the Vespertine conglomerate, or sandstone, occupies an extensive irregular area 
between the escarpment of the Alleghany Mountain on the S., the State line on the N., the 
valley of the North Branch of Susquehanna on the E., and the waters of the Sinnemahoning on 
the W. Throughout the rest of the region, the Coal-measures bordered by the Serai conglome- 
rate occupy the whole surface. The beautifully symmetrical structural features of this vast region 
are illustrated in the general Sections. Viewed broadly, the whole territory is to be regarded as 
only the north-eastern end of an enormous coal-basin, which, commencing in our northern 
counties, has its southern termination in Middle Alabama. The portion which is embraced 
within the limits of Pennslyvania, covers more than 10,000 square miles. It has for its south- 
eastern margin, the narrow table-land of the Alleghany Mountain ; and for its northern border, 
the much wider plateau of the northern counties. From these two limits, the surface slopes 
south-westward, sinking gradually towards the middle of the vast but nearly horizontal trough. 



120 



SUBDIVISIONS OF PALEOZOIC KEGION. 



Traversing nearly the whole length of this district are five very long and comparatively low 
or fiat anticlinal undulations, which subdivide the general area into six subordinate narrow coal- 
basins. 

The First of these lesser basins is bounded in Somerset by the anticlinals of Negro Mountain 
and Laurel Hill. It thence follows the table-land of the Alleghany Mountain, and ends at the 
North Branch in the narrow plateau of the Mahoopeny Mountain, the trough gradually ascending 
and fiattening until finally it is greatly denuded of its coal-measures, as it approaches its north- 
eastern termination. 

The Second Basin, or that of Ligonier Valley, is in its southern parts a deep trough, between 
the anticlinals of Laurel Hill and Chestnut Eidge. It rises and shoals towards the N.E., and as a 
continuous coal-basin terminates on the V^est Branch of the Susquehanna, below Karthaus. 
Further on it becomes a table-land, ending in a narrow elevated spur near Towanda, and sustain- 
ing, like the eastern end of the first basin, only a few detached small patches of the coal-rocks. 

The Third Basin beo-ins near the Kiskiminetas, and rises toward the Sinnemahonius;, until 
at Trout Eun it ceases to contain a continuous belt of the Coal-measures. It there merges into 
the general northern plateau, and is prolonged into Bradford as a third narrow mountain-spur, 
sustaining a few insulated tracts of the Coal strata. South of the Kiskiminetas there are 
three sub-basins in the prolongation of this third synclinal belt. 

The Fourth Basin likewise commences near the Kiskiminetas, and ceases to hold any but a 
few small patches of Coal strata beyond the sources of Trout Eun. It ends in a long narrow 
plateau or flat spur in the northern part of Tioga County. 

The Fifth Basin originates as a defined trough of the Coal-rocks in the neighbourhood of 
Freeport, by the rising of the anticlinal axis which forms its north-western limit. This basin 
contains an unbroken belt of Coal-measures as far as Clarion Eiver. Following the valley of 
that stream toward its sources, it becomes a part of the general northern table-land. Though it 
retains the synclinal form, only its higher summits hold any tracts of the Coal strata, and even 
these scattered patches cease after the belt enters Potter County some distance. Its north-eastern 
prolongation is rather a chain of low, flat, sandstone hills, than an unbroken spur or plateau. 
South-westward it merges into the larger basin of the Ohio Eiver. 

The Sixtli Basin is the last or north-western trough, formed by the general south-eastward 
dip of all the strata from their north-western outcrop, and by the fifth anticlinal. It is of great 
breadth in Butler, Beaver, and Mercer, but contracts and grows shallow in Clarion and Elk, and 
becomes a mere chain of detached coal-bearing summits resting on an elevated plateau of the 
Serai and Vespertine sandstones and conglomerates, as it ascends the Tionesta into Warren and 
M'Kean counties. In the opposite or south-western direction, this trough enlarges by the merg- 
ing into it of some of the narrow adjacent basins on its S.E., and it becomes the main coal-field 
of the Ohio Eiver for a great distance along the western border of Virginia and the south-eastern 
side of Ohio. 

Besides the above six long subordinate troughs included in the general Coal-field, there is one 
to the east of the first enumerated, occupying the south-eastern side of Somerset County, between 
the anticlinal axis of Negro Mountain and the crest of the Alleghany Mountain. The northern 
end of the Potomac Basin of Virginia and Maryland penetrates a few miles into Pennsylvania. 



NINTH DISTRICT. 



121 



There is a small high synclinal belt, containing, however, little or no available coal, in the 
table-land of the Alleghany or Bowman's Mountain, in Luzerne County. This may be viewed as 
a portion of the first or Mahoopeny Basin. 

Taking a comprehensive view of the whole broad bituminous Coal region, we are struck with 
the extraordinary length, parallelism, evenness of breadth, and progressive declension north-west- 
ward of its several beautiful belts of symmetrical, anticlinal, and synclinal waves, and with their 
strong resemblance, in all the features here named, and in their grand crescent-like sweep, to a 
group of subsiding billows. • 

When we enlarge our survey still farther, and embrace the entire width of the Appalachian 
flexures from the south-eastern to this north-western side of the State, we are still more forcibly 
impressed with this resemblance, and with the appropriateness of the general theory of crust- 
undulations elsewhere given. In the south-eastern division of the State, the strata are, for the 
most part, closely folded or plicated, the north-western sides of the anticlinals being entirely 
inverted : in the middle or mountain region, this feature is somewhat subdued ; the waves are 
more expanded, though still steep and of the unsymmetrical form ; while in this north-western 
district, the undulations are low, and much dilated, and the two slopes of each wide wave are 
approximately equal. 



VOL. I, 



Q 



CHAPTEE III. 



DISTEIBUTION OF THE PALEOZOIC STRATA IN PENNSYLVANIA, AND THEIR 
CHANGES OF TYPE AND THICKNESS. 



Before entering on the detailed delineation of the Palaeozoic Eocks, in their many successive 
outcrops within the State, it will be expedient, for the sake of completing our general picture of 
them, to show their broader features, with the changes of type and thickness which they undergo. 
Beginning with the lowest, and pursuing each formation in the geographical order laid down, or 
from S.E. to N.W., we shall commence with the Primal series. 



PEIMAL SEEIES— South of Chester Valley. 



90 



Primal Lower Slate. — This formation is developed in great thickness from the Braudywine to the Susquehanna, 
and thence south-westward, but is too much disguised by metamorphism, and close plication of its beds, to admit of 
measurement. It is, indeed, nowhere susceptible of exact estimation, but may be conjectured to be, where most 
expanded, ............. 2000 feet. 

Prijial Sandstone. — This rock, the equivalent of the Potsdam Sandstone of New York, is distinctly 
visible, though not in much thickness, around some of the small limestone basins of Chester County. It is 
prominent on the Street Road, and in Dochranaman Hill; hnt its thickness is not accurately ascertainable. It 
occurs on the Susquehanna, the most southern outcrops being near Peach Bottom, where it measures 

Primal Upper Slate. — This formation is not recognisable around the limestone troughs of the southern 
part of Chester County. 

The Primal Lower Slate, — 

On the Schuylkill, consists of two divisions : — 

1st, Tlie Lower, a semi-porphyroidal altered sandy slate, is 
2d, Tlie Upper, an imperfectly crystallised talcose micaceous slate, is 
In Edgeliill, near Attleborough, the formation measures 
Primal Sandstone. — This frequently consists of two sandstones and an interposed slate. 
Thicknesses — 

On Schuylkill and Wissahickou, 35 to . 
East of Willow Grove (including quartzose conglomerate), 

Edgehill, near Attleborough, ....... 

Coatesville, North Valley Hill — 

Lower Sandstone, . . ...... 

Slate, . . 

Upper Sandstone, . . . . 



15 feet. 
70 „ 
40 ., 



Parheshurg, North Valley Hill — 

Lower Sandstone, .... 
Slate, ..... 
Upper Sandstone, .... 

Smquehanna, above Columbia- 
Lower Sandstone (with included bands of slate). 
Slate, ..... 
Upper Sandstone, .... 



50 
300 
20 



300 
300 
27 



300 
200 
200 



40 

100 
300 



125 



370 



627 



PRIMAL SERIES. 



123 



Primal Upper Slate — in line of Chester Valley. 

At Willow Grove, and east of it, this rock does not exist. 

In Barren Hill, and on the North Pennsylvania Railroad, it is talcose and thin. 

At the Diamond Rode, and in Paoli Section, it is thin, possibly between 200 and . . . 300 feet. 

Near Coatesville it is . .... ... . . 700 „ 

At Parkeshurg, where probably all is not seeuj it shows ...... 300 „ 

On the Susquehanna, above Columbia, it measures about ...... 1000 „ 

From the above data it would appear that this division of the Primal series augments even more rapidly than the 
White Sandstone as it stretches westward. 

Survey of the Formation — The Primal White Sandstone fluctuates much as to its thickness 
within the region where it occurs, though it is singularly retentive of its character as a rock. 
It would seem on the whole to augment towards the S.W. or W. ; and this agrees with its 
general absence in New Jersey, and its full dimensions on the western slope of the Blue Eidge 
in Virginia. 

The Primal Upper Slate likewise increases westward and north-westward, as the preceding 
statements fully indicate. We know, moreover, that it is in great force in Maryland and 
Virginia. 

PEIMAL SEEIES— IN the South Mountains. , 

On the Delaware River — 

The Prblil Sandstone is the principal formation of the series, very little slate being discernible. 

In Durlmm Ridge, at Myer's Quarry, its whole thickness is about . . . . . 1 00 feet. 

In Chestnut Hill, north of Easton, the sandstone is well developed, but its thickness is unknown ; probably 
it does not exceed ........... 100 „ 

On the Schuylkill, below Reading — 

Its thickness is much greater than at the Delaware. 

It is folded and criished, and cannot be measured. 
The Primal Slates possess some development in the South Mountains near the Schuylkill, but cannot be 

measured. 
In Adams County — 

Both of the Primal Slates, particularly the Lower, are evidently largely developed in the South 

Mountains, between the Susquehanna and the Potomac. 
The Primal Sandstone is also thick throughout this belt, probably as thick as on the Susquehanna, or 300 „ 
The Primal series nowhere rises again to the day N.W. of the South Mountains. 

AURORAL SERIES. 

Auroral Calcareous Sandstone. — A rock apparently identical with the true Calciferous Sand- 
stone of New York, is visible near the Delaware, and at a few points further W., along the south 
margin of the Kittatinny Valley, as at Columbia, but nowhere throughout this belt in much 
thickness. Assuming that the lowest sandy Magnesian Limestone of the Auroral series at 
Columbia represents this formation, it has there a thickness, between the underlying Primal 
slate and another overlying slate, of 250 feet. 

No fossils having been discovered in it, we have only lithological characters to guide us, and 
its identification is therefore doubtful. 

A calcareous friable sandstone, unlike the Primal sandstone, rises from beneath the Auroral 
limestone in the more elevated tracts of Nittany Valley and Morrison's Cove, and I have less hesi- 
tation in referring it to the Auroral calcareous sandstone. Still no fossils have been found in it, 
though no favourable outcrops have occurred. 



124, 



TYPES OF PALEOZOIC STRATA. 



AURORAL MAGNESIAN LIMESTONE. 

This great formation, wliicli seems to constitifte the most extensive floor of the Appalachian 
Basin east of the Missouri Eiver, is nowhere in Pennsylvania susceptible of entire measurement. 
In its south-eastern synclinals, as the Chester and Conestoga valleys, we have its lower part, but 
not its upper. In the Kittatinny Valley, though the whole formation is present, it is too much 
plicated and obscured to admit of satisfactory mensuration ; and in the great anticlinal vaUeys 
of Centre, Blair, and Bedford, though its entire thickness outcrops in certain neighbourhoods, 
it is impossible, from the extensive wash from the sandy barrens against which it rests, to 
ascertain, within a few hundred feet, its lower limit. In these last districts we may, however, 
make an approximation to its total bulk. 

On the Schuyll-ill its upper and lower portions are not visible, or are so concealed as to make estimation of thickness 
impossible. It is, however, practicable to obtain proof of great thickness, by measuring across the limbs of the synclinal 
basin from its contorted central area. The measurements thus made serve to check each other, and give a thickness of 
3000 feet, comprising evidently the middle and a large part of the lower beds of the formation. The limestone is of the 
Magnesian type, somewhat argillaceous in the upper beds. 

In Kishicoquillas Valley the lower beds are not visible for perhaps many hundred feet. 

1. The lowest seen are alternations of light-blue, fine-gi'ained, and darker magnesian rock, with knots of white 



dolomite, ....... 300 feet. 

2. Fine-grained light-greyish blue magnesian limestone, — a little chert in lower layers, 600 „ 

3. Dark crystalline magnesian limestone, with kernels of dolomite, . . 100 „ 

4. Light-blue limestone, weathers mealy, conchoidal fracture, . . 600 „ 

5. Slightly magnesian limestone, some beds very pure ; fine texture, purplish blue, 

massive and ribboned, ...... 200 „ 

6. Pure light-blue conchoidal and massive limestone, . . . 150 „ 

Total thickness visible, . 1950 feet. 

Nittany Valley, Bellefonte, ascending — 

1. Grey crystalline rough magnesian limestone, underlaid by much of same con- 

taining chert, visible, ...... 600 „ 

2. Pure blue limestone — no fossils, ..... 700 „ 

3. Grey crystalline limestone, no fossils, .... 1500 „ 

4. Light-blue fine-grained, like bird's-eye marble, a very few characteristic fossils, 300 „ 

5. Alternation of light and dark-grey rough crystalline rock, weathers with sandy 

surface (not silicious), corals and other fossils, . . . 1000 „ 

6. Magnesian, massive light-blue grey — no fossils, . . . 500 „ 

7. Alternation of blue coralline and argillaceous dull-blue magnesian limestone, 200 „ 

8. Dark-blue massive rubbly limestone, with many fossils, . . 400 „ 

9. Clear blue, massive, like bird's-eye marble, with fossils, . . . 150 „ 

10. Massive, blue, fine-grained limestone, with obscure corals, . . 20 „ 

11. Blue, thin-bedded limestone, encrinal and coralline, . . . 30 „ 

Total thickness, . 5400 feet. 



MATINAL SEEIES. 

The Matinal series is evidently thick wherever it appears in Pennsylvania, and has apparently 
its maximum dimensions at its great south-eastern outcrop, in the Kittatinny or Appalachian 
Valley. There, however, its thick uppermost mass, the Matinal shale, is unfortunately so folded 
and so intersected with cleavage-planes as to bafile every attempt at measurement. The whole 
series cannot be of much less depth than the Auroral limestone, and we shall not err widely if we 
assume it, in the Kittatinny Valley, at from 3000 to 4000 feet. 

The Matinal shale manifestly declines in thickness as it spreads north-westward, but the other 
members — the black slate and the argillaceous limestone — appear to retain their bulk. 



MATINAL SERIES. 



125 



MATINAL LIMESTONE (Trenton L. op New York). 

No traces of this formation have been met with in either of the great limestone basins S. of 
the Kittatinny Valley. Within that long limestone belt it appears and disappears, at intervals, 
from the Delaware River to Maryland, though probably it is absent through more than two- 
thirds of this distance. 

Delaware Rivtn: — The forrricatiou has been measured ouly on Martin's Creek, near the road leading from Easton 
to the Delaware Water-Gap. There it is -n-ell exposed, and exhibits its characteristic composition and fossils. Its 
thickness is about 350 feet. 

KishicoquiUas Vallei/.—The next outcrop of the formation admitting clear measurement is Kishicoquillas 
Valley, about half-way across the Mountain Chain. Here, under its usual type of alternating thin layers of 
smooth dark-blue limestone and blue shale, and with its usual fossils, it has a thickness of . . 550 „ 

Nlppe)iose Fo^^e-y.— Advancing to the furthest north-western outcrop, the Matinal limestone appears through- 
out nearly the whole length of the Great Nittany Anticlinal, where the elevation is sufficient to bring it to the 
day. In Nippenose Valley, with numerous characteristic fossils, the rock graduates at its upper limit into 
the Matinal black slate. It measures . . . • • • • • • 300 „ 

Fittany Valley.— In the neighbourhood of Bellefonte, a more south-western locality on the same belt, the 
Matinal limestone, in the condition of a bluish-grey, thin-bedded, but somewhat rubbly limestone, has a total 
thickness of . . . . • • ... . . . . 360 „ 

The lowest 60 feet is dark-blue, thin-bedded, and of the Trenton type. 

Millikms Cove. — Far to the S.W. the Matinal limestone is discernible in Millikeu's Cove and the other 
limestone coves of Bedford County. It wears its usual type, and has the characteristic fossils, but is obviously 
of reduced thickness, when compared with its development N. of the Juniata. 

MATINAL SLATE (Utica Slate). 

Kittatinny Valley.— 'The first or most S.E. appearance of the Matinal black slate is in the Kittatinny 
Valley, where it occurs chiefly between the Delaware and Lehigh. On Martin's Creek, where it is finely 
exposed, it measures about .......... 300 „ 

It grows thinner proceeding westward. Near Nazareth it is very carbonaceous, and at its outcrop is so soft 
as to be convertible into a pulverulent, dark pigment. 

Kishicoquillas Valley. — This formation is well developed around the borders of nearly all the anticlinal 
limestone valleys of the Mountain Chain west of the Susquehanna. It is of full dimensions in Kishicoquillas 
Valley, where it is of its usual composition, but much intersected with cleavage. It measures, apparently, 400 „ 

It is recognisable by its Graptolites and other distinctive fossils. 

Nippenose Valley. — In this anticlinal uplift the Matinal black slate abounds in its usual fossils, retains all 
its lithological characters, and exhibits a thickness of . . . . . . . 300 „ 

Nittany Valley. — Near Bellefonte, and elsewhere along the N.W. border of the last gi'eat anticlinal, the Black 
slate, with its characteristic fossils, measures nearly ....... 300 „ 

Milliken's Cove. — It occurs as far S. in the State as Milliken's Cove, with its usual fossils and in its full dimensions. 
The passage between its lower limit and the top of the underlying limestone being, as elsewhere, quite abrupt. 

MATINAL SHALES (Hudson River Slate). 

As already stated, this, by far the largest formation of the Matinal series, is not susceptible 
of accurate measurement anywhere along the Kittatinny Valley, its main south-eastern outcrop. 
Eeappearing all round the anticlinal limestone valleys between the Kittatinny and Alleghany 
Mountains, S.W. of the Susquehanna, it there displays itself in numerous good exposures. 

Kishicoquillas Valley. — In Kishicoquillas Valley, the locality selected as being about half-way across the chain, the 



126 



TYPES OF PALEOZOIC STRATA. 



formation occurs under its usual Pennsylvanian type of a blue shale and slate, alternating with thin grey calcareous 
sandstones, and containing many distinctive fossils, especially towards its upper limit. It has a total thickness of 
about . . .......... 1200 feet. 

Nittany Valley. — Crossing north-westward to its last oiitcrop in the State, we find this rock ranging along 
the south-eastern base of the Bald Eagle Mountain, under an average thickness of about . . 700 ,, 

An imperfect measurement in Nippenose Valley indicates its thickness there to be a little less, and in Bedford County 
it is perhaps somewhat greater. 

Summary. — The whole formation presents a marked reduction in thickness as it spreads west- 
ward, or more properly north-westward ; but in crossing the Mountain Chain of Pennsylvania, it 
exhibits no approach to the highly calcareous t}^e which it wears where it next re-emerges to the 
day in the distant anticHnal of Southern Ohio and Northern Kentucky. 

LEVANT SEEIES. 

The Levant series, naturally divisible into three groups or distinct formations, is largely 
developed in the Appalachian Chain of Pennsylvania, from the Kittatinny Mountain, its most 
south-eastern outcrop, to the Bald Eagle Mountain, Dunning's Mountain, and Wills' JMountain, 
its most north-western. Each of the subdivisions undergoes a greater or less change of type in 
advancing across the Chain ; indeed, the middle member, or red shale and sandstone, does not 
show itself at all in the Kittatinny Mountain and other south-eastern outcrops ; and the lower 
and upper formations, likewise thin towards the S.E., acquire their maximum development 
near the opposite side of the Mountain Zone. These Levant sandstones constitute, with the 
exception of the carboniferous sandstones enclosing the Broad Top Coal-field, all the mountain- 
ridges, and higher spurs, of the entire Chain west of the Susquehanna between the Kittatinny 
Valley and the valley at the base of the Alleghany Mountain. 

Within this space a remarkable series of long, parallel, anticlinal undulations of the strata 
lift these rocks into the mountain-crests alluded to. In the part of the Chain occupied by 
Perry, Juniata, Mifflin, Union, and Centre counties, the chief anticlinal mountain outcrops of 
the Levant series are about nineteen in number ; while in the district south of the L^pper 
Juniata, or that of Franklin, Huntingdon, Fulton, Bedford, and Blair, their outcrops amount 
to seven or eight. 

With a view to avoid a too detailed tracing of the changing characters and dimensions of 
the three members of the Levant series, they will be described in this general sketch as they 
occur only in their south-eastern, middle, and north-western outcrops in the Chain. 

LEVANT GREY SANDSTONE (Oneida Conglomerate of New York). 

Kittatinny Mountain or South-Eastern Outcrop — Delaware Water-Gap. — At this locality the inferior group of the 
Levant series is very thick. It consists of two members. The lower is a grey sandstone and conglomerate, the 
pebbly beds most abundant near its base ; the upper strata are formed of finer-gi-ained light-grey sandstone, with part- 
ings of light fissile slate. Whole thickness about .... . . 300 feet. 

The second member is a softer sandstone, chiefly thin bedded, and in colour greeuish-grey. Its thickness 
is about ............ 400 „ 

Neither of these rocks contains any fossils. 

Total thickness, . . . 700 „ 



LEVANT SERIES. 



127 



Lehigh TTa^er-G^aj).— The next good exposure of the formation is at the pass of the river Lehigh. There the 



mass consists — 

1st, Of -very coarse quartzose conglomerate, . ... . . . .50 feet. 

2d, An alternation of fine white sandstone and a nut coarse conglomerate, capped by a still coarser, . 75 „ 

3d, A coarse quartzose conglomerate, with beds of sandstone, . . . . . . 75 „ 

4th, Fine-grained white and grey sandstone, fiue conglomerate, and layers of shale, . . . 200 „ 



Total thickness of the formation, 400 „ 



StLsquelmnna Gap. — The strata referable to this member of the Levant series at the Pass of the Susque- 
hanna are, near the base, a very coarse heterogeneous red conglomerate, not more than 5 feet thick ; and in 
contact with this, a compact white conglomeritic sandstone, in thickness not more than 40 feet. The sand- 
stone exhibits oblique slips or faulty joints, and may originally have been somewhat thicker than it now 
measm-es. There is likewise a blank space between the southern limit of the conglomerate and the northern 
visible limit of the Matinal shale, amounting to between 40 and 50 feet more, and possibly a portion of this is 
occupied by beds of the Levant series. But making every allowance, we cannot attribute to this grey sand- 
stone formation a greater total bulk than from GO to , . . . . . . 70 „ 

Comparing the three exhibitions of this stratum in the Kittatinny Mountain, it presents a remarkable 
reduction of size as it extends south-westward. But this feature is perfectly in accordance with what we know 
of the relations of the formation to the series upon which it reposes further to the N.E. in New York. There 
it rests unconformably upon the upturned edges of the Matinal strata ; a fact which, taken in connection with 
its coarse, pebbly heterogeneous composition, shows that to have been the quarter of greatest disturbance of 
the sea-bed, at the time of the strewing in of its materials. It is easy, therefore, to understand how those 
materials should have been accumulated more abundantly than in the remoter localities to the S.W., where 
the agitations of the earth's crust were gentler. 

J ad's Motmfain, or Middle Belt, Kishicoquillas Gap. — Advancing now about half-way across the chain to 
the middle belt of outcrops, the first good exposure of the formation admitting of measurement is at the 
Kishicoquillas Gap in Jack's Mountain. The position of Montour's Ridge in Columbia County would make 
a comparison between the formation at that locality and the Kittatinny Mountain interesting ; but unfor- 
tiinately it is inaccessible to observation, the lowest rock visible in the anticlinal axis being an ixpper member 
of the Levant white sandstone group. 

Contenting ourselves with the developments in Jack's Mountain, we have, at the Kishicoquillas Gap, the 
Levant grey sandstone, in the condition of a fine-grained, light-grey, massive sandstone, abounding in yellow 
ferruginous specks. It has here a total thickness of . . . . . . . 300 „ 

Juniata Gap, or Jack's Narrows. — At this locality the stratum is a greenish white, hard, silicious sandstone, 
with a total thickness of . . . . . . . . . . 250 „ 

Comparing the two exposures in J ack's Mountain, we observe the same reduction of the formation south- 
westward that we have previously noticed in the Kittatinny Mountain ; a further confirmation of the view 
adopted, that the materials of this deposit were swept in from the N.E. or E., and not from the S.E., as was 
the case with some of the other Appalachian rocks. The formation displays, however, an obvious augmenta- 
tion of thickness, when we contrast it in this middle belt with its diminutive btdk in the Kittatinny Mountain 
opposite. 

Bald Eagle and Wills Mountains, or North- Western Outcrop, Belief onte Gap.'—HhsxQ is no sufficiently complete 
exposure of the Levant grey sandstone admitting of measurement, in the Muncy and Bald Eagle Mountain, 
until we advance as far to the S.W. as the Gap near Bellefonte. At this spot there are two groups of strata, 
the lower, a hard grey sandstone without pebbles, but full of the characteristic yellow specks, its thickness 
being 170 feet; and an upper, composed of greenish-grey slightly micaceous sandstone, with the ochreous 
specks, and divided by thin layers of a fissile greenish slate, under a thickness of 380 feet. Possibly the upper 
member should belong to the Levant red sandstone, or middle formation of the series; but its characters 
place it rather in the grey sandstone. Thus constituted, the formation measures . . • 550 „ 

Canoe Mountain Gap, J uniata This locality is not quite on the line of the most north-western out- 

crop, but is near enough for general comparison. All the Levant formations are well exposed here. The 
grey sandstone wears its usual character of a grey-greenish and pinkish hard silicious sandstone, in massive 
beds. Its thickness amounts to nearly 500 ,, 



128 



TYPES OF PALAEOZOIC STRATA. 



The next outcrop eastward exhibits the formation at Water Street in Tussey Mountain, under a thickness 
of ............ . 450 feet. 

Wills' Mountain, Milliheii's Cove. — The last locality at which this rock is to be seen, to the S.W. along its 
north-western outcrop, is in the main gap entering MiUiken's Cove of Wills' Mountain. There the rock, as 
visible, measures only about . . . . . . . . . . 100 ,, 

Looking at the very notable difference in its thickness here, when compared with that on the Juniata, one is dis- 
posed to suspect an obscuration of the lower portion of the mass, from a possible fault along the western edge of 
MiUiken's Cove ; a conjecture sviggested by the vertical and shattered condition of the strata in Buffalo Ridge, the 
western barrier of the Cove. Should this not be the case, the formation has undergone an unusually sudden diminution 
in its bulk. We are nevertheless warranted in looking for some abatement of thickness towards this south-western 
quarter. 

General Survey of the Formation. — It will be seen, upon scanning the facts here recorded of 
the Levant Grey Sandstone, that while it displays a marked declension of size from the Delaware 
to the country west of the Susquehanna, or in the direction of its first outcrop, and exhibits a 
corresponding, but less notable declension in the same south-west direction along its middle and 
north-western belts, it presents, in a transverse or north-west direction across the Chain, an 
almost equally rapid augmentation of its bulk. We may look upon the successive anticlinal and 
synclinal outcrops and undulations of the stratum as but portions of a deposit originally con- 
tinuous, from some unknown limit south-east of the Kittatinny Mountain to an undefined north- 
western or western boundary, where the oceanic waters of the Levant period ceased to deposit 
their materials. Within the mountain-range, where alone this broad sheet of matter has been 
lifted to view, or where lifted, preserved in the general denudation, we discover a progressive 
enlargement of its mass within the Chain, both eastward and north-westward, indicating some 
north-easterly quarter as the direction of its maximum average expansion. There can be little 
doubt that, after the tremendous crust-movement which j)artially upheaved and drained the bed 
of the Matinal ocean, the trend of the newly-established shore of the contracted waters was 
N.E. and S.W., and the sea-shore itself at no great distance S.E. of the Shawangunk and 
Kittatinny Mountain. And it is a fair deduction from all the assembled facts, that the first strong 
currents at least of the Levant period, or that strewing the grey sandstone, came from the N.E., and 
spent themselves south-westward and westward. We have evidence in the stratification of Vii-ginia 
that it carried its materials far south of the* Potomac ; but how far in a westerly direction it 
swept them out into the mid-sea, which existed where w^e have now the great coal-basin of 
Western Pennsylvania and Ohio, it is beyond the power of man to divine. The wide anticlinal 
uplift of Ohio, Middle Kentucky, and Tennessee, brings the Matinal shales conspicuously 
to the surface, but shows them immediately overlaid by the Scaleut rocks, and in some places 
by yet higher formations, enabling us to perceive that there was not a vestige of the sediments 
of the Levant period deposited so far towards the W. And this conclusion is confirmed when 
we pass still further across the floor of the ancient Palieozoic sea, and discover a similar total 
absence of the Levant materials at the upper limit of the Matinal shales in Wisconsin and 
Missouri. 

LEVANT EED SANDSTONE (Medina Red Shale of New York). 

It has been already intimated that the Levant Ked Sandstone has no existence, so far to the 
S.E. as the Kittatinny Mountain. It first shows itself in the south-eastern part of the Mountain 
Chain to the west of the Susquehanna, in Perry and Franklin counties. The formation becomes 



LEVANT SERIES. 



129 



for the first time conspicuous in the Tuscarora Mountain, being cut into on the anticlinal axis, 
at the pass called Run Gap. It is feebly developed in the ridges enclosing Path Valley. In the 
long complex anticlinal belt, or group of anticlinal mountains, the Shade, Blue, and Black Log 
mountains, this formation is still more expanded, forming there, wherever the denuding waters 
have cut the series deep enough, a disti*Qct bench or terrace below the level of the higher crest. 
But no good exposure offers itself in this zone for measuring the thickness. We must, therefore, 
select the nearly central outcrop, or that of Jack's Mountain, for the first distinct development, 
admitting of satisfactory observation of the type and thickness of the stratum. It has been 
already intimated that this rock does not show itself in Montour's Eidge, the elevation and erosion 
of the strata there not having proceeded quite far enough. 

JacFs Mountain, Kishicoquillas Gap. — At this most north-eastern exhibition of the Levant Red Sandstone, it consists 
of three members, the lowest a pale, red sandstone, imbedding pebbles of qnartz, Matinal slate, and other older Appala- 
chian rocks, 400 feet in thickness, snrmounted by a coarse, friable red sandstone, sprinkled in some layers with small 
pebbles, and full of large ferruginous spots, 100 feet thick ; and this overlaid in turn by a dark-red, flaggy, and in part 
argillaceous sandstone, containing in some layers pebbles of red shale ; thickness 500 feet. The total thickness of this 
well-characterised formation is thus, at this locality, about ...... 1000 feet. 

Juniata Gap, or Jack's Narroivs. — Here the rock is a red argillaceous sandstone, speckled yellow with 
hydrated peroxide of ii-on, and alternating with red shale. The sandstone beds abound in oblique lamiuaj, or 
false bedding. Thickness .......... 650 „ 

North-western Outcrop, Bald Eagle Mountain, Bellefonte. — The most north-eastern locality along its north- 
western outcrop, at which the Levant Red Sandstone has admitted of measurement, is the Bellefonte Gap. Tliere 
it is a thin bedded grey and red argillaceous sandstone, alternating with a fourth part red, grey, and greenish 
shale. High in the mass are found stem-like vegetable forms resembling an irregular Scolithus. This appears 
to be the Scolithus vertical is of Hall, a fossil of the Medina Sandstone of New York. The thickness of the rock 
here is about ........... 500 „ 

Canoe Mountain Gap, Juniata River. — At the gap of Canoe Mountain this rock is a reddish brown, rather 
argillaceous sandstone, with beds of grey sandstone, all alternating with much red shale. Here its thickness 
is expanded to .......... . 1050 „ 

In the next south-eastern outcrop of Tmsey Mountain, at the gap called Water Street, the whole mass, 
possessing the Scime general composition, measures . ..... 700 „ 

Millikens Cove. — At this locality, which is upon the same general line of outcrop, the rock holds its prevail- 
ing north-western characters, except that it includes a larger amount of grey sandstone than on the Juniata. 
Its thickness is .......... . 800 „ 

General Survey of the Formation. — Comparing the data afforded by the above records, we 
perceive that this formation, while it dilates rapidly in thickness as we meet it going northward, 
exhibits at the same time, at its successive outcrops, a fluctuation in its dimensions. The direc- 
tion of its maximum increase would seem to be nearly westward on the parallel of the Juniata 
Eiver ; but we are not in possession of a sufficiently numerous and widely-dispersed series of 
measurements to deduce any general inferences respecting the direction of its more permanent 
development, or the quarter from whence its sediments have entered this portion of the ancient 
Appalachian Sea. 

LEVANT WHITE SANDSTONE (part of Medina Group of New York). 

The upper formation of the Levant Series, a somewhat complex grou^) of white sandstones 
and olive-coloured slates, ranges, as already indicated, with the lower or grey sandstone through 
the entire breadth of the Appalachian Chain, from the Kittatinny Mountain to the Bald Eagle 
and Wills mountains. Of the three Levant formations, it is altogether the most fluctuating 

VOL. I. R 



130 



TYPES OF PALAEOZOIC STRATA. 



as respects its subdivisions or general type, though in regard to its thickness it is apparently 
the most constant. The fluctuations it undergoes result from the coming in and thinning out of 
some, or nearly all, of its sandstones and slates. Perhaps the most persistent of its members is 
a mottled red and white hard sandstone, in comparatively thin layers high in the formation, well 
characterised by impressions of the Ai'tlirophycus Harlhni. This a]3pears to be the typical rock 
of the Medina Sandstone of New York. 

Kittatinny Mountain, or South-Eastern Outcrop — Delaware Water-Gap. — Selecting the same localities as those previously 
chosen for exhibiting the other formations of the Levant Series, we shall commence with this at the Delaware Water- 
gap. It here consists of a light-grey and olive-grey compact sandstone, in some beds sparsely pebbly. This member, 
forming a prominent rib of the mountain, is about 200 feet thick. Overlying this are some alternating beds of sandstone 
and slate, bxit whether these are properly referable to this formation, or to the lower part of the overlying Surgent series, 
is somewhat imcei'tain, the outcrops being obscure. 

Lehitjh Water-Gap. — At the Lehigh Water-Gap there is a thick succession of alternating white sandstones and olive 
shales, the upper sandstones being mottled red and white, and containing the characteristic Marine vegetation. There 
is a deficiency of exposiires in the lower part of the formation through more than 200 feet, though the fragments indicate ^ 
both grey sandstone and the olive-coloured shales. There then succeeds a white and grey pebbly sandstone, 80 feet thick. 
Above this repose alternating greyish white sandstones and brownish sandy shales, about 100 feet thick, overlaid by 
white sandstone and brownish and green slates, vaguely marked by fucoids 50 feet thick, succeeded by sandy shales, 
brown, olive, and yellow, 30 feet thick. Capping these are olive and buff, green and brown shales, with grey and greenish 
flaggy sandstone, 300 feet thick. These bring us to the uppermost bed of the formation, which is a massive red and 
grey quartzose sandstone, intercalated with olive and yellowish shales, the whole group having a thickness of 100 feet. 

The aggregate bulk of the formation is therefore about ...... 760 feet. 

Susquehanna Gap. — It is impossible, from the lack of clear exposures of the strata, to determine with preci- 
sion the other different members or the total thickness of the Levant White Sandstone formation at the Susque- 
hanna. It is sufiicieutly obvious, however, that it consists there, as elsewhere, of an alternation of white sand- 
stones, with greenish and yellowish slates, and that it has reddish sandstones, with marine plants among its 
upper layers. Its total thickness may be estimated at from 300 to .... . 400 „ 

This formation, so obviously below its average size in the south-western part of the Kittatinny Valley, 
augments steadily as we meet it rising in its successive anticlinals through Perry, Juniata, and Milflin counties, 
in crossing north-westward. As only its uppermost members are visible in Montour's Ridge, at the Danville 
NaiTows, it is impossible to estimate its bulk in the middle belt of the chain to the east of the Susquehanna j 
but westward of the river it has been measured at all the localities already given as exposing the other two 
lower Levant formations, except the Kishicoquillas Gap. 

J acJcs Mountain, South-East Flank — J uniata Gap, or Jack's Narrows. — At this interesting locality the 
Levant White Sandstone is composed, 1st, Of two principal massess, the inferior a white and greenish-grey 
silicious sandstone, generally massive and very compact, with scai-cely a trace of organic remains, its thick- 
ness being 420 feet ; and, 2d, Of a red sandstone, alternating with grey and pinkish sandstone, and green and 
red shale, only 30 feet thick. The uppermost, or thin member, has some of its sandstone layers covered with a 
network of the Arthrophi/cus Harlani. Total thickness of formation ..... 450 „ 

North-Westem Outcrop — Bald Eagle Mountain — BeUefonte. — Here the Levant White Sandstone has its 
usual composition, and though not measurable with perfect precision, its thickness is evidently between 400 and 500 „ 

Canoe Mountain-Gap of the Juniata. — Here the formation is a i-ather homogeneous mass of white and grey 
fine-grained sandstone in ponderous beds. Its thickness, cai'efully measured, is . . . 550 „ 

At the Gap of Water Street, in Tussey Mountain, with a similar composition, the thickness of the mass is 500 „ 

At both localities the Arthrophycus Harlani abounds near the top of the formation. 

Milliken's Cove. — In the Buffalo Ridge, the western barrier of this anticlinal valley, the Levant White 
Sandstone exists, well exposed under its prevailing north-western homogeneous type. Its thickness here is 
about ............. 400 „ 



Genei'dl Survey of the Formation. — At the Susquehanna, and also at the Delaware Water-Gap, 



SURGENT SERIES. 



13] 



the Levant White Sandstone is too vaguely defined in composition and limits to permit us to 
trace its changes in the Kittatinny Mountain. We are able, however, to recognise it, especially 
at the Lehigh Water-Gap, as possessing in this its south-eastern outcrop its most complex type. 
Contrasting the aspects of the rock here, and in the central belt, it manifestly becomes more aren- 
aceous as it spreads north-westward, from a diminution of its shales, which at the Lehigh greatly 
preponderate over the sandstones, and from a positive and rapid augmentation of the latter. The 
upper part of the formation retains its mixed type of olive shales, and close-grained white sand- 
stones, as far even as Jack's Mountain; for in the belt next to the S.E., or that of the Shade and 
Black Log ridges, the alternation of these is conspicuous. The Pennsylvania Canal is excavated 
in this alternating upper division of the formation through the Long Narrows of the Juniata. It 
is an interesting fact that this series is nearly constant in its thickness throughout its middle 
and north-western outcrops. It is to this uniformity of bulk, and to its equally remarkable 
permanency of composition and hardness, that we must ascribe the extraordinary evenness of 
height and width in the sandstone crests of all this portion of the mountain-chain. 

While speaking of the Levant grey sandstone, it was shown that none of the formations of 
the Levant period reach westward to the anticlinal of Ohio and Kentucky ; but casting a glance 
northward to the geology of the basin of Lake Ontario, we can discern the western limits of each 
of the three formations, under the names of the Oneida Conglomerate, Medina Shale, and Medina 
Sandstone, the Oneida Conglomerate extending no farther than the eastern end of Lake Ontario, 
the Medina Eed Shale and its overlying sandstones running on across the Niagara River, and 
thence north-westward nearly to the Straits of Mackinac. 

From these statements it is obvious that the Middle and Upper formations, deposited in 
more tranquil waters, were much more widely diffused, both south-westward and north-westward, 
than the coarser, more heterogeneous grey sandstone beneath them; the red shale, the finest sedi- 
ment of aU, spreading the farthest distance. 

SUEGENT SERIES. 

The Surgent group of formations, like the Levant series, with which it is intimately con- 
nected, is in great force throughout the Appalachian Chain of the State, from the north-west 
flank of the Kittatinny Mountain to the similar slope of the last Main Eidge east of the foot of 
the Alleghany Mountain. It consists of seven formations or sub-groups of strata, and each of 
these varies in its type and thickness within the space described, independently of the others. 
Some of them, indeed, are altogether wanting in the Kittatinny Mountain, and other south- 
eastern outcrops. As these Surgent rocks adjoin those of the Levant series immediately beneath 
them, they observe almost precisely the same topographical distribution ; the chief difference 
being, that whereas the Levant usually form the crests of the synchnal ridges, these constitute one 
flank and base of the monoclinal ones, and both slopes of the anticlinal. They likewise stretch 
away in tapering belts, from the terminal spurs of the mountains, some distance forward into 
the plains. 

SURGENT LOWER SLATE (base of Clinton Group of New York). 
South-East Belt, or Kittatinny Mountain and Perry County. 

At the Delaware Water-Gap this formation is too obscm-ely visible to admit of measurement or description. 



132 TYPES OF PALAEOZOIC STRATA. 

At the Lehigh Watei'-Gap it may be distinctly recognised and measured, having a thickness of about 100 feet. 
In Ferry County it exhibits its usual type of a fissile, olive-coloured slate, becoming claret and 

liver-coloured by exposure. It measures from 150 to . . . . 200 „ 

Middle Belt. 

At Mifflintowii the Surgent lower slate, olive-coloured and fissile as usual, measures . 150 ., 

At Danville it is a greenish slate, weathering yellow, and containing bands of a block iron ore. It 

measures apparently ....... 700 „ 

At the south-east base Jack's Mountain, JacFs Nari-ows, &c., this formation is not separable fi'om 
the Surgent upper slate, owing to the absence of the iron sandstone, the two together consisting 
of. A, green slate, with a few thin calcareous layers ; B, yellow and olive slate, with very little 
calcareous matter, but some thin, sandy beds J measures from 500 to . . 550 „ 

North- West Belt. — Milton, and north-west of the Muucy or Bald Eagle Mountain. 

Along this outcrop all the three members of the Surgent slate gxoiip are present ; but the exact posi- 
tion and thickness of the Surgent iron sandstone are not easily ascertainable. The whole group 
measures ........ 700 „ 

Survey of the Formation. — This member of tlie series appears not to fluctuate much in the 
north-east and south-west direction, but it undergoes a marked increase of thickness towards the 
N.W. Beyond the Appalachians, however, it is again, upon its reappearance at the surface in 
New York, much thinner, being seldom more than 50 feet. 

SURGENT IRON SANDSTONE. 

South-East Belt. 

At the Delaware Water-Gap this rock has escaped notice, if indeed it exists. 

At the Lehigh Water-Gap its thickness is . . . . • .4 feet. 

In Perry County, in the Kittatinny Mountain, it is . . . ' . . 80 „ 

It is thinner further N.W. 
Middle Belt. 

Near Miffiintown it is a ponderous red and brown ferruginous sandstone, with partings of slate. It 

contains trails or tracks of some animal. Its thickness is from 20 to . . . 25 „ 

Near Danville it is an alternation of olive sandy slate, and brown heavy sandstone, containing the 

block iron ore. It measures . • • • • "^^j? 

At Jack's Mountain it is absent. 

On the Potomac it is 3 or . . . . • • • 4: „ 

In Wills Creek Axis it is . . • • • • -30 „ 

North-West Belt. — This rock is present in the north-west outcrop, but its thickness is unknown. 

Survey of the Formation. — This rock, seldom more than 50 feet in thickness, appears to 
observe no law of regular development in any given direction, but, like many other of the 
Appalachian sandstones, fluctuates variously. 



SURGENT UPPER SLATE. 

South-East Belt. 

At the Delaware this rock exists apparently in much force, but cannot be easily measured. 

Near the Lehigh Water-Gap this slate passes so insensibly into the Surgent lower shale, that the two 

must be measin-ed together. Their thickness amoimts to about • • • 166 feet. 

In Perr^ 6'o««^;/, under the form of a dingy olive slate, it measures . . . 100 „ 

Middle Belt. 

Near Miffliutmvn it is a green and claret-coloured slate. Its only fossils are faint fucoids. It 

measures from 200 to • -'^^ » 

Near Danville the formation is a green fissile slate. Thickness . . • • 50 „ 



SURGENT SERIES. 



133 



In JacVs Mountain it is not separable from the Surgeut lower slate, through the absence of the iron sand- 
stone. 
North- West Belt. 

Here, though separated from the Surgent lower slate, it is not independently measurable. 

Survey of the Formation. — Like the Surgent lower slate, of which it is hut a repetition, this 
stratum augments towards the N.W. through the mountain-chain. 
On the Potomac the two slates measure together al30ut 400 feet. 

SURGENT LOWER SHALE, 

South-East Belt. 

It is doubtful if the lower and upper shales exist at the Delaware Water-Gap ; their fossiliferous iron ores have 
never been discovered. 

Near the Lehigh Water-Gap the lower shale, though present, is so united with the upper slate as not to admit 
of separate measurement. 

In Perry Countij this formation is imperfectly developed ; the calcareous fossiliferous layers are but 
little seen, even at Millerstown. The fossiliferous ore is barely recognisable. The whole measures, 
probably, . . . . . . . .100 feet. 

Middle Belt. 

Near Miffiintmvn it is a liver-coloured calcareous slate, imbedding thin layers of sand}^ fossiliferous 

limestone. Thickness uncertain. 

Near Danville it is composed of green fissile shale, fossiliferous limestone, and fossiliferous iron oi'e. 

Total thickness, ... ..... GO feet. 

In Jaclcs Mountain it is an olive and claret-coloured fossiliferous shale, with occasional thin layers of 

calcai'eous and argillaceous sandstone. It measures 200 to ... 250 „ 

North-West Belt. 

In the north-ivest outcrop this formation is a greenish shale, with sandy calcareous layers — thickness 110 „ 

Survey of the Formation. — It would seem that this stratum first enlarges somewhat in spread- 
ing towards the N.W. across the mountains, and then contracts again to about its original 
thickness. 

SURGENT ORE SANDSTONE. 

South-East Belt. 

At the Lehigh Water-Gap) this formation is easily recognised. It measures . . 110 feet. 

In Perr;/ Coifw^y it is a close, hard, white sandstone — thickness, . . . 15 ,, 

In the south-east part of the county the iron ore underlies, in the north-west it overlies, and in 
some places it lies both below and above, the ore sandstone. 
Middle Belt. 

Near Miffiintoimi the ore sandstone measures 20 to . . . . . 25 „ 

Near Danville it is a tough calcareous sandstone — thickness, . . . . 8 „ 

In J^ffcA:'s il/oz(?itojn the ore sandstone measures . . . . . 25 „ 

North- West Belt. — Here this formation is absent. 

Survey of the Formation. — Thickest towards the east ; this rock, west of the Susquehanna, 
gradually thins away north-westward, but with fluctuations. 
On the Potomac it is 30 feet. 



SURGENT UPPER SHALE. 

South-East Belt. 

Ai the Lehigh Wate)'-Gap it m&ixmxeH . . . . . . 120 feet. 



134i 



TYPES OF PALEOZOIC STRATA. 



In PetTy County this fornication is a calcareous olive shale ; it weathers buff, and contains the fossiliferous ore. 
It measures in the S.E. 30 to 50 feet, in the N.W. 150, and has an average thickness of . 50 feet. 
Middle Belt. 

Near Miffiintoion. — Here it is composed of grey calcareous shale, with thin layers of fossilferous lime- 
stone — thickness 200 to . . . . . . . 225 „ 

Near Danville it is a sandy, argillaceous, green fissile slate, with layers of fossiliferous limestone, and 

fossiliferous ore near the base — thickness, . . . . .160,, 

In Jack's Mountain it is composed of altered olive calcareous shales, and thin beds of limestone. The 

lower beds of the latter are fossiliferous, while the upper beds are not so ; it measures . 250 „ 
North-West Belt. 

The upper calcareous shales consist, ascending, of — 
- 1. An alternation of slates and ferruginous limestones, with some fossiliferous iron ore, 60 feet. 

2. Olive and buff shales, . . . . . . G5 „ 

3. Limestone with Beyrichia, . . . . . . 65 „ 

4. Grey and greenish shale, full of fossils, . . . . . 40 ,, 

Total, . — 230 „ 

Survey of the Formation. — This Upper Calcareous Shale group appears to enlarge gradually 
towards the N.W. Both it and the Lower Shale are, however, much thinner at their distant 
outcrop in Clinton County, New York, than in Pennsylvania, both masses there being seldom 
more than 20 feet thick. 

On the Potomac the two shales together measure about 340 feet. 

SURGENT RED SHALE — MARL. 

South-East Belt. 

At the Lehigh Water-Gap this formation is abundantly developed. It has a thickness of about 975 feet. 

In Perry County, at the Susquehanna Gap, it measures .... 400 „ 

Middle Belt. 

Near Mifflintoivn, where it contains the Clinton fucoid, or Butliotrephis gracilis, its thickness is . 340 „ 
Near Danville it is a uniform red shale, without fossils, and measures . . . 380 „ 

In Jacl's Mountain the red shale exists in full development, but its thickness is undetermined. 

It measures at Newton Hamilton, ...... 250 „ 

And at Lewiston, about . . . . . . . 160 ,, 

On the Potomac, at the Capon Axis, it is about . . . . . 100 ,, 

North- West Belt. 

Here the Surgentred shale maintains its usual constant characters. It is without fossils. Its thick- 
ness is . . . . . . . . . 350 „ 

In Blair and Bedford it is much thinner, and at the Potomac, near Cumberland, it is wanting entirely. 

General Survey of the Formation. — It would seem, from the above local measurements, that 
the Surgent red marl or shale steadily thins towards the south-west, and at the same time 
towards the north-west, but much more gradually. In the latter direction it appears in New 
York, near Lake Ontario, but reduced to a very slender deposit. 

SCALENT SEEIES. 

This series, the representative, in a general way, of the Onondaga-Salt and Niagara groups 
of New York, consisting, in Pennsylvania, of three subdivisions or formations, is in some districts 
of the Appalachian Zone in very great force. Its usual topographical position is in the valleys 
at the feet of the high monoclinal and anticlinal ridges of the Levant sandstones, and on the 
adjacent sides of the neighbouring limestone ridges. The Niagara limestone, so important a 
formation in New York and the North- Western States, is absent from the series in Pennsylvania; 
but the Water-lime exists, and is very persistent throughout the Chain. 



SCALENT SERIES. 



135 



SCALENT VARIEGATED MARLS. 

South-East Belt. 

At the Kittatinny Mountain it is not seen. 

Near the Tiiscarora Mountain, where the stratum first appears in force, its thickness is about . 100 feet. 
Middle Belt. 

Near Neivton Hamilton, where it consists of an alternation of red, bluish, and greenish shales, and 

thin layers of argillaceous limestone, it measures ..... 285 „ 

On the Potomac at the Capon Axis, it is about ..... 300 „ 

At MiJlinto7i'n it exceeds . . . . . . . . 440 „ 

At Leu'istovm about ........ 450 „ 

North- West Belt. 

Near Muncytown this stratum is an alternation of red and green marl. It is only . . 20 ., 

Survey of the Formation. — This deposit exhibits a rather remarkable increase of thickness 
from the S.E. to the Middle Belt of the Appalachian Zone, and an equally remarkable decrease 
thence north-westward. 

SCALENT GREY MARLS. 

South-East Belt. 

At base of Kittatinny Mountain very feebly developed. 

Near Tiiscarora Mountain it is a mass of grey, greenish, and bluish calcareous shales, in thickness 

about . ........ 600 feet. 

Middle Belt. 

Near Miffiintown, it measures about . . . . . . 600 „ 

Near Lewistown, about ....... 500 „ 

Near Newton Hamilton, consisting, in the lower part, of green and blue calcareous shales ; in the 
middle, of the same, with flaggy limestone ; and in the upper, of flaggy limestone, alternating 
with grey, blue, and olive calcareous marls. It measures . . . . 945 „ 

On the Potomac it is about . ...... 350 „ 

North- West Belt. 

Near Milton this formation consists of blue shales and thin layers of limestone, with thicker beds 
of blue fissile slate, underlaid by a thick succession of greenish and bluish marls, alternating 
with flaggy, argillaceous limestones. It contains few or no fossils. Its thickness is . 1200 „ 
From Muncy south-westward, the formation grows gradually thinner and less diversified. 

Survey of the Formation. — West of the Susquehanna the Surgent grey marls seem to enlarge 
in bulk steadily towards the N., and more slowly towards the N.W., or they gradually dechne 
south-westward. 

SCALENT LIMESTONE, 

South-East Belt. 

At the Kittatinny Mountain this rock is absent altogether. 

In the centre of Perry County its average thickness is .... 

At the Tuscarora Mountain it is . . . . . . 

Middle Belt. 

k.t Mifflintown it exposes, perhaps, more than . . ... 

At Newton Hamilton, where it is a flaggy blue limestone, supporting 25 feet of chert, it measures 
At Lewistown it is thicker. 

On the Potomac the thickness is about ...... 

North-West Belt. 

Near Milton, this rock, a thin-bedded blue limestone, with Cytherina alt a and other fossils, has a 

thickness of . . . . , . . . 

Between Muncy and Jersey Shore it is from 40 to . . . . . 



50 feet. 
200 „ 

30 „ 
85 „ 

350 „ 



100 „ 
60 „ 



136 



TYPES OF PALEOZOIC STRATA. 



At Franhstoion, where it is a blue flaggy limestone, imbedding chert between its upper layers, it measures 
more than ........ 215 feet. 

Survey of the Formation. — With considerable fluctuation this hmestone appears to augment 
gradually south-westward, for in Blair and Bedford it is frequently thicker than 200 feet, and 
we have seen that it is still thicker on the Potomac. 

PRE-MEEIDIAN SEEIES. 

This remarkably persistent calcareous group of shaly and massive Limestones, with more or 
less Chert, is almost everywhere present west of the Susquehanna, where the undidations of the 
strata lift the middle Palaeozoic rocks to the surface. Its orographic position is usually near 
the crests of the monoclinal ridges which next adjoin the mountains of the Levant sandstones, 
the very crests themselves carrying the overlying ]\Ieridian sandstone. Its distribution and 
changes of type appear from the following details : — 

PRE-MERIDIAN LIMESTONE. 

South-East Belt. 

Along the Kittatinny Mountain the formation is in some places quite thick ; in others very attenuated, or 
gone altogether. 

At Broadheads Creek, near the Delaware Water-Gap, it is a dull, blue, hard, and massive limestone, 

imbedding chert in its upper part. It abounds in corals. Thickness, . . 105 feet. 

At the Susquelianna Gap there appears to be no trace of it. 

At MiUerstown it measures ....... 100 „ 

At the Tuscarora Axis, the limestone is . . . . , . 140 „ 

The overlying chert, . . . . . . . . 25 „ 

It occurs here in two divisions, both fossiliferous — 

A lower massive one, . . . . . ■ . . . 60 „ 

An upper thin-bedded one, . . . . . . . 80 _., 

In Fulton County, its average thickness is about ..... 250 „ 

Middle Belt. 

Along this line the formation expands south-westward, but with fluctuations. 

In Montour's Ridge it is . . . . . . . 60 „ 

Between Lewistown and Newton Hamilton, where it is a blue massive encrinal and coralline lime- 
stone, it is . . . . . . . . 107 „ 

At the Potomac, above the mouth of tlie Capon, it is . . . . . 2-t „ 

The Pre-meridian chert varies from nothing to 30 feet, or more, being in Montour's Ridge thin and 
absent ; west of Adamsburg, 30 feet ; at Newton Hamilton, 0; and on the Potomac, 20 to 30 feet. 
North- West Belt. 

Near Muncy this rock is in its lower part a massive encrinal limestone, containing corals and 

other fossils, and is from 140 to . . . • • . 150 „ 

On the Juniata at Frankslown it is a massive blue and knotty limestone, with a bed of shale in the 

middle: its thickness is . . . . • . . 135 „ 

Survey of the Formation. — With many fluctuations of thickness, but great general constancy 
of type, this rock rather augments in mass as we approach the Potomac. North-westward it is 
not thick, ranging from 20 to 50 feet in the valley N.W. of the Bald Eagle Mountain. 

At its outcrop in the Helderberg Mountain, in New York, its thickness varies from 100 to 
140 feet. South-westward along the Appalachian Chain this rock maintains its full bulk of 200 
or 250 feet. 



MERIDIAN SERIES. 



137 



It seems not to spread to the western outcrops of the Appalachian strata in Middle Kentucky, 
Ohio, or beyond Western New York. . 

MEEIDIAN SEEIES. 

This coarse and fossiliferous sandstone, with its frequently attendant shales, is one of the 
most constant of all the Palaeozoic strata in Pennsylvania. It is rarely altogetlier absent ; for 
even where, from its feeble cohesion and comparative thinness, it exposes no conspicuous out- 
crop, we may usually detect its presence at the places appropriate to it in a yellow sand derived 
from its disintegration. When in force, it usually occupies the crest of the narrow, sharp, stony 
ridges which next adjoin the high sandstone mountains of the Levant series. 

MERIDIAN SLATE. 

South-East Belt. 

At the Tuscarora Axis, on the Susquehanna, this rock is chiefly the dusky, calcareous, sandy shale, and its 
thickness is . . • . . . . . 80 feet. 

In the middle of Ferry County it is about . . . . . . 40 „ 

At the base of the Kittatinny Mowitain it is . . . , . wanting. 

From the Delaware to the Susquehanna, along the base of the Kittatinny Mountain, it fluctuates 

from 0 to . . . . . . . . 100 feet. 

Middle Belt. 

In this zone these sandy slates and shales, though variable, are thickest towards the N.E. Thus — 

Near Danville, they are . . . . . . . 30 „ 

Near Newton Hamilton, as friable sandy shales, from 40 to . , . . 50 „ 

On the Potomac they are . . . . . , . wanting. 

North- West Belt. 

In Whitedeer Valley these dusky shales, passing upward into argillaceous sandstone, measure about 70 feet. 
Near Muncy the type is that of a dusky shale, weathering buff", the upper beds sandy and 

cherty, the thickness . . . . . . . 60 „ 

Between Muncy and Lockhavcn, . . . . . . . 50 „ 

At Franlcstoivn, on the Juniata, the formation embraces two divisions — 

1. Dark ash and black slate, without fossils, . . . .80 feet. 

2. Dark grey, sandy, calcareous shale, with fossils, . . . 90 „ 

170 „ 

Survey of the Formation. — This interesting formation expands very slowly northward rather 
than north-westward. It does not appear to exist in New York, nor in any of the Western 
States, but it seems to run on south-westward into Virginia. 

MERIDIAN SANDSTONE. 

South-East Belt. 

This formation, conspicuous and easily traceable wherever it possesses even a moderate thickness, is occa- 
sionally discernible N.W. of the Kittatinny Mountain, as near the Lehigh Water-Gap, in the crest of the 
first stony ridge. 

At the Lehigh, where it is a pebbly sandstone, its thickness is 80 or . . . 90 feet. 

At the Susquehanna it is . . . . . . . wanting. 

In Perry County, where it is frequently a pea-conglomerate, it is nowhere more than . 20 feet. 

Middle Belt. 

Along this zone the formation augments in thickness south-westwai-d, but unsteadily. 

In Montour's Ridge it is in some places hardly visible ; in others it is . . . 35 feet. 

From the Susquehanna to Lcivistown it expands to , . . . . 70 ,. 

VOL. I. S 



138 



TYPES OF PALAEOZOIC STRATA. 



Near Newton Hamilton, where it is a massive, coarse calcareous sandstone, imbedding layers of chert in 
its lower portion, it measures . . . . . . 150 feet. 

On the Potomac its dimensions are about ...... 350 „ 

North- AVest Belt. 

In Whitedeer Valley it is . . . . . . . very thin. 

Traced along this belt, the sandstone increases in thickness south-westward from Muncy to Franks- 
town, and thence declines to the Potomac. 

Near Frankstoion, where it is a calcareous fossiliferous sandstone, internally bluish, externally 

yellow, it measures . . . . . .,125 feet. 

Survey of the Formation. — As already stated, this formation fluctaates, but it is in the main 
thickest westward and south-westward. It does not range into Western New York, but stretches 
along the Appalachian Chain far through the State of Virginia. It is not seen in Eastern or 
Middle Tennessee, nor anywhere west of the Appalachian Coal-field. 

POST-MERIDIAN SERIES. 

The formations of this series nowhere appear in Pennsylvania, except in the valley north-west 
of the Kittatinny Mountain, between the Walpack Bend of the Delaware and the Lehigh River ; 
it is unnecessary, therefore, to trace their distribution in this place. 

CADENT SERIES. 

The Cadent formations, some of which are among the most astonishingly persistent of aU the 
Appalachian Palseozoic deposits, occur in superb development in many portions of the Mountain- 
chain of the State. Topographically considered, they occupy the sides of the long synclinal 
and monoclinal valleys south-west of the Susquehanna, and the more central parts of some of 
the anticlinal valleys or plains outside of the outer ridges confining the Anthracite Coal-fields. 
These three formations, the Lower and Upper Black Slate, and an interposed Olive Shale, undergo 
but few changes of type, except that of thickness ; but this being a material element, its varia- 
tions in regard to each must be noted separately. 

CADENT LOWER BLACK SLATE. 

Sotjth-East Belt. 

Along the valley N.W of the Kittatinny Mountain this formation is, for the most part, very thin, or alto- 
gether wanting. 
At the Stisquekamia Gap its thickness is quite insignificant. 
In Perry County, it consists, at the Half- Fall Mountain, of — 

1. Buff and grey Calcareous Shale, imbedding a minute plant, . . 25 feet. 

2. Pale-green Argillaceous Limestone and Green Shale, . . . 20 „ 

3. Black fissile Carbonaceous Slate, full of the usual fossils, . . .180,, 

Total thickness, . . 225 feet. 

Middle Belt. 

Along this zone the deposit is somewhat inconstant in its thickness, though very persistent in its 

composition, excepting as to its iron ore. 
Near Selinsgrove, on the Susquehanna, it measures . . . . . C65 ., 

It is there a black fissile pyritous slate with layers of impure limestone. 
At Lewistown it is several hundi-ed feet thick. 

On the Potomac, near Sideling Hill, it is an ash-coloured and black slate, passing upward into black 

fissile slate and impure clayey limestone. Its thickness is . . . . 59U ,, 



CADENT SERIES. 



139 



North-West Belt. 

lu the AVhitedeer Valley this formation is a fissile black slate, with large lenticular cakes of blue limestone 
and septaria in its lower half. These become more continuous further S.W. Its fossils are few. The 
thickness here is from GOO to . . .... 800 feet. 

Near Frankstown it is a black fissile slate, with cement layers near its base. Its thickness is more 

than . . . . . . . . . 300 „ 

On the Potomac it measures upwards of . . . . . . 400 „ 

Survey of the Formation. — -It undergoes a marked expansion northward in the Apjialachians, 
and a much less rapid augmentation south-westward along the Chain, as far at least as the Poto- 
mac and interior of Virginia, beyond which it steadily diminishes, to disappear in Eastern 
Tennessee. It is probably wanting altogether in the Western States, the Black Slate of the 
west appearing to be the Cadent Ujiper Slate. 

The thick layer of impure argillaceous limestone accompanies this slate near its base, in 
Fulton and other neighbouring counties. 

CADENT SHALES. 

SODTH-EAST BeLT. 

This formation ranges parallel with the Kittatinny Mountain, from the Delaware Eiver to Perry County, as 
a mass of grey and olive shales, growing gradually sandy until, between the Schuylkill and the interior of Perry, they 
become an argillaceous sandstone, with even some silicious conglomerate. This sandstone character, however, fades 
rapidly north-westward, and ceases between the Tuscarora and Shade mountaius, the rock assuming its normal compo- 
sition of a true shale or fine sandy mud. 

Along the south-east side of Per>"_y this rock is . . ... 800 feet. 

In the Half-Fall Mountain on the Juniata, where the formation is a hard fossiliferous sandstone, it 

measures between 600 and ....... 700 „ 

Middle Belt. 

On the Poto?>i«c the formation is at its maximum, or . . . . . 1100 „ 

North- West Belt. 

In Wliitedeer Valley, where the rock is an argillaceous and calcareous blue sandy shale and sand- 
stone, with numerous fossils, its thickness is from 600 to . . . . 800 „ 
Between Frankstown and the foot of the Lock Mountain it is . . . . 400 „ 
From HolUdayshurg, south-westward, the formation grows very thin. 

At Cumberland, on the Potomac, it is . . . . . . wanting. 

Survey of the Formation. — This formation, the Hamilton Group of New York, increases in 
its average thickness to the Potomac, and ranges thence south-westward along the Appalachian 
Chain, until it expires near the James Eiver in Virginia. In the AVestern States this middle 
deposit of the Cadent period appears to have no existence. 

CADENT UPPER BLACK SLATE. 

South-East Belt. 

On the Leliiijh, north of the Kittatinny Mountain, the Calcareous Upper Black Slate is seen under a thickuess 
of from 220 to . . . . . . . . 250 feet. 

In Perry County the rock is altogether . ..... wanting. 

Middle Belt. 

On the Potomac this rock measures ...... 415 feet. 

North- West Belt. 

Throughout this belt the deposit is usually a bluish-black fissile slate, with minutely-divided par- 
ticles of mica, and a small sagitate fossil. 
In Whitedeer Valley it measures 200 to . . . . . • 300 „ 



TYPES OF PALEOZOIC STRATA. 



In the il/wnry ZTzW*, and north-eastward, 250 to ..... 300 feet. 

Near Frankstown, it is from 300 to . . . . . . 350 „ 

On the Potomac, near Cumberland, it is not less than .... 700 „ 

Survey of the Formation. — This very widely-diffused deposit of ancient black Carbonaceous 
Mud appears to augment pretty steadily in a westward direction across tlie Chain. In Virginia 
it appears to attain its maximum near the James Kiver, having a thickness on Dunlap's Creek of 
850 feet. It thins away altogether in Eastern and Middle Tennessee. Westward along the 
northern outcrop of the great Appalachian Basin, it stretches through New York, Ohio, and Indi- 
ana, into Northern Illinois, where it comes gradually to a thin feather-edge. From the best 
authorities it reappears, however, far to the N.W., in British America. 

VERGENT SERIES. 

This series, consisting of two closely -related formations, a group of flaggy Sandstones and 
Shales, and a group of Fossiliferous Shales, occurs at every large outcrop of the middle Palaeozoic 
strata within the State. The two formations observe somewhat opposite directions for their 
maximum development, and must therefore be traced separately. They occur, for the most part, 
ranging centrally along the synclinal and monoclinal valleys embraced between the Mountain 
Ridges, composed of the Levant sandstones on one or both sides. 

VEEGENT FLAGS. 

South-East Belt. 

These rocks may be recognised on the Lehigh under a somewhat more than iisually argillaceous type. Some 
of the thin flaggy layers are imprinted with the trails of molluscs and other marine creatures. The thickness of the 
formation here has not been ascertained. 

In Ferry County this group is . . . , . . . wanting. 

Middle Belt. 

Near Catawissa the formation, with its characteristic fucoids or marine plants, appears under a 

thickness of . . . . . . . . 1000 feet. 

Near Z/wn<2n^c?on it is a little thicker, being about . . . . . 1700 „ 

On the Potomac it is again less developed, being about . . . . 1200 „ 

North-West Belt. 

Along this line of outcrop, at the base of the Alleghany Mountain, the thickness of the gi'oup, as 

well as its characters, are very constant. 
At the ITfisi ^ranc/t of the Susquehanna it is about . .... 1200 „ 

At Hollidayshurg it is a little thicker. 

At the Potomac it is ....... 1400 or 1500 „ 

Along this line the mass consists of dark-grey flaggy sandstones, parted by thin layers of blue shale. 
Large marine plants, and a Nucula, are its chief fossils. 
Fourth Belt. 

In Prac//br(Z and Tf'of/a counties the Vergent Flags are . ... 1000 „ 

On the Genesee River, in New York, it measures about . . . . 1000 „ 

There the deposit consists of thin-bedded, fine-grained, silicious grey sandstones, intimately alter- 
nating with blue and greenish shales. 

Survey of the Formation. — This formation appears to augment slowly towards the N., the W., 
and the S.W. 



VERGENT SERIES. 



141 



VEEGENT SHALES. 

South-East Belt. 

On the Lehigh, the whole Vergent series, consisting chiefly of this group, measures about . 1750 feet. 
In PeiTij County the Vergent shales consist of two members, — 

1st, A lower, composed of olive-grey and blue shales and grey sandstones, with a dark slate 

at the bottom : this is about . . . . . . 1 700 „ 

2d, An upper, of brown shale and sandstone, alternating with grey shale and sandstone, . 700 „ 
Middle Belt. 

At Catawissa this deposit — an alternation of grey, red, and olive sandy shales, with grey and red 

argillaceous sandstones — has a thickness of . . . . . 3050 „ 

Near Huntingdon this formation, not very fossiliferous in type, has a thickness of . . 3200 „ 

North-West Belt. 

On the Portage Railroad, and extensively along the base of the Alleghany Mountain, the average 

thickness of the formation is not far from . . . . . 2200 „ 

On the Patomac, a few miles east of Cumberland, its thickness is between 2100 and . . 2400 „ 

Fourth Belt. 

Between Mahoopeny and Tioga Poiilt it is apparently . . ... 2500 „ 

Fifth Belt. 

On the Genesee River, New York, it is . . . . . . 1500 „ 

Survey of the Formation.— ThiQ very thick formation, remarkable for its general uniformity 
of composition, appears from the above statements to liave its maximum development in the 
region of the Juniata, or half-way across the Appalachian Chain. Though it gradually thins 
towards the W., it is a rock of wide extension in that direction, spreading into Ohio, Kentucky, 
and Middle Tennessee, and along the Appalachian Chain. It stretches in full force through 
Virginia, and reaches East Tennessee, and probably Alabama. 

PONENT SERIES. 

The Ponent strata of the Appalachian Chain constitute a thick and remarkably uniform 
deposit, which does not admit of subdivision, either by its fossils or its mineral composition. 
Unlike some of the great groups, which gradually assume new phases, by the loss or the acquisi- 
tion of subordinate members, or by mutations in the members they retain, this series undergoes 
almost no important modification but that of thickness. Adjoining, as it does, the overlying 
Vespertine sandstone, which, from its bulk and superior hardness, almost invariably occurs in the 
shape of a high ridge, this Ponent group occupies generally the slope and foot of the Vespertine 
mountains. Thus it forms the south-eastern flank and base of the main Alleghany Mountain 
throughout its entire course across the State. And it everywhere falls into a like position in the 
exterior or Vespertine Mountain ridges which encircle the whole anthracite Coal region. The 
formation exhibits a very interesting gradation in its dimensions as it spreads through the State, 
which the following details will show. 

South-Eastern Belt. 

It has its thickest development at its first or south-eastern outcrop, or in the A'alley N.W. of the Kittatinny 
Mountain. 

At the Lehigh River it measures . , . . . . , 5000 feet. 

At the Susquehanna it is about ....... 6000 „ 

Middle Belt. 

Throughout this belt the character of the deposit — which may be accepted as a fair type of the formation 



TYPES OF PALEOZOIC STRATA. 



generally — is that of a red sandstone and red shale, containing, in their superior portion, gi-ey and buff sandstones, 
alternating with grey and yellow shales, all surmounted by a conglomeritic rock, of a fine-grained red sandstone paste, 
imbedding pebbles of white quartz. No good exposures for measuring the Ponent rocks occur between Catawissa and 
the Potomac. 

At Catawissa the formation measures . . . . . . 4172 feet. 

On the Potomac, in Sideling Hill, its thickness is about . . . . 4500 „ 

North- West Belt. 

Its average thickness along the Alleghany Mountain may be assumed at about . . 2000 ,, 

Around the Wyoming Basin it is approximately . .... 2-500 „ 

Near Tunhhannoclc, whei'e it preserves its middle type, being free fi-om very coarse grits, and con- 
sisting of fine and argillaceous sandstones, Avith an increase of red and green shales, and with 
some calcareous layers, it measures about ..... 1500 „ 

On the Loyal Sock Creek its thickness is nearly . . ... 1000 „ 

Fourth Belt. 

Near Ralston it is between 550 and . . . . . . 600 „ 

In the Armenia Mountain, on the Williamsport and Elmira Railroad, it is . . . 400 „ 

On Towanda Creek, above Canton Corner, an approximate measurement shows it to be nearly 400 „ 
Fifth Belt. 

In the Tioga Valley, near the State line, according to the Geological Survey of New York, its thick- 
ness is . . . . . . . . . 400 ,, 

Near Ellisburg, between Coudersport and Wellsville, New York, it measm-es only . . 90 „ 

It consists in this district of greenish, sandy shale, red mai'ly shale, and very thinly bedded mica- 
ceous and shaly sandstone. 
Near /S»ie</;/)orHts probable thickness is somewhere near . . . . 170 „ 

In this district the deposit consists of red marly shale, and a bright green ferruginous sandy shale 
and argillaceous sandstone, forming a red soil. A curious dark, rough, pebbly rock occm-s in 
the red shale. 

Near Clean, N. Y. — In the valley of the Alleghany River, south of Olean, the Ponent mass — chiefly a 

red shale — has an apparent thickness of . . . . . . 50 ,, 

At Warren. — No trace of the Ponent formation is visible around Warren, nor any red shales refer- 
able to the series. Here the Alleghany River flows outside, or west of its western margin. 

Survey of the Formation. — From the foregoing statements it is obvious that this great homo- 
geneous deposit thins away steadily and rapidly towards the N.W., from its maximum develop- 
ment at its south-eastern outcrop, near the Susquehanna River. This abatement of the mass is 
regular and not fluctuatiupi;, a fact which confirms the inferences to be deduced from its unifor- 
mity of composition ; namely, that it was deposited all from one quarter, and during one long 
uninterrupted condition of the physical geography. From Pennsylvania the formation may be 
traced south-westward along the Appalachian Chain, with a gradual declension of size, until it 
finally thins out in eastern Tennessee. Dipping westward from the Appalachian Chain under the 
first great bituminous coal-field, it nowhere reappears at its western margin, but evidently ceases 
somewhere in the interval ; nor does the formation, nor any equivalent of it, reappear any- 
where in the Western States. 

VESPERTINE SERIES. 

The Vespertine group of strata, the first of the carboniferous formations of the Appalachians, 
has a very wide distribution in Pennsylvania, encircling with a sort of outer girdle all the coal- 
fields, both the anthracitic and the bituminous ones, of the State. It undergoes gradual but 



VESPERTINE SERIES. 



143 



important changes of type, growing thinner and assuming a finer and finer texture in its materials 
as it spreads westward. Its orographic position is in the mountain-ridges and external escarp- 
ments of the table-lands which enclose or support the coal-fields ; but, except in the north-western 
district of the State, it does not immediately adjoin the conglomerates and sandstones of the coal- 
measures, but is separated from them by a greater or less thickness of the soft, umbral rocks, 
which fill either an intervening valley or an intermediate space on the coal-bearing table-lands. 
South-East Belt. 

This great formation is thickest and most varied in its composition along its south-eastern outcrops, or where 
it surrounds tlie first antliracite coal-basin. 

At Mauch Chunk, on the Lehigh, its thickness is . . . . • 1-300 feet. 

Near Pottsville the mass is about ....... 1800 „ 

In the Second Mountain, on the Susquehanna, and in the Fourth, or Peter^s Mountain, opposite Dun- 
cannon, it measures nearly ....... 2000 ,, 

Throiaghout this belt it consists largely of coarse grey sandstones andsilicious conglomerates, with 
grey shales imbedding coal plants. 
Middle Belt. 

In the Nescopech Mountain, north of the eastern Middle Coal -basins, the formation measures . 1100 „ 
At Ca<aw('ssa, in the same line of outcrop, it is . . . . . 1044 „ 

Wyoming Basin. 

Surrounding the northern or Wyoming Coal-field, the Vespertine series consists of a succession of 
grey sandstones, imbedding some pebbly layers and some beds of shale. It has everywhere a 
thickness of several hundred feet. 

At CohUs Gap, where it is made up chiefly of greenish-grey sandstones, it measures . . 310 „ 

At Solomon's Gap, where the greenish-grey sandstone is more argillaceous, and subdivided by more 
numerous and thicker layers of shale, and where the whole terminates upward in a stratum of 
coarse pebbly and micaceous sandstones, the entire mass possesses a thickness of about 560 „ 

At Hertzog's Gap, north of Kingston, the Vespertine series consists chiefly of olive and reddish sand- 
stones and shales, with occasional layers of a coarse grey sandstone ; the uppermost 80 or 
100 feet include a mass of thick-bedded grey sandstones, passing towards the centre into a 
coarse conglomerate. The entire series measures here nearly . , . 600 „ 

North- West Belt. 

\ii the Alleghany Mountain, on t\ie Loyal Soch, it^ t\nc\.neii& IS . . . . 900 „ 

East of the North Branch it is much thinner. 

In this North-west Belt, and along the north side of the State, it is a somewhat argillaceous, 

micaceous flaggy sandstone. 
Near Wellsborough the Vespertine deposit amounts to . . . . . 700 „ 

Fourth Belt. 

At the Conemaugh Gap, S.E. base of Laurel Hill, the Vespertine formation is a grey sandstone with 

beds of shale, terminating upwards in a grey calcareous sandstone ; its thickness is 400 to 500 „ 

On the Conemaugh Gap, at the western slope of Chestnut Ridge, the rock is a grey argillaceous and 

micaceous sandstone, with a few beds of dark shale. Its thickness is . . . 349 „ 

Near Astonville this formation is a greenish, flaggy sandstone, with beds of grey sandstone and blue 

slate. Its thickness is . . . . . . . 475 „ 

At the Hill at Cartersville, 1| miles above Ealston, only the top of the Vespertine is seen. 

At Blossburg the Vespertine sandstone consists of greenish and grey argillaceous sandstones, with a 
thin calcareous concretionary bed about 30 feet from the bottom. The whole formation pos- 
sesses a thickness of . . . . . . . 150 „ 

Fifth Belt. 

In the vicinity of Coudersport, retaining its prevailing north-western type of greenish and grey 

sandstone, it seems to have a thickness of about ..... 300 „ 



U4 



TYPES OF PALAEOZOIC STRATA. 



It is very probable that a portion of tbis, perhaps the upper half, is to be ranked as umbral. An absence of 
fossils and a close assimilation in the types of the two series, render it difficult to define their com- 
mon boundary. 

Olean. — In the hills, three miles and more S. of Olean, the Vespertine Series, consisting of evenly- 
bedded greenish-grey sandstone, with partings of olive shale, measures about . . 100 feet. 
It contains sx ScoUthus, or vertical worm-like form. 

Warren. — Around this locality the group of rocks reposing directly upon the easily recognisable 
Vergent series, and overlaid by the Serai White Sandstone, and therefore referable to the Ves- 
pertine series, consists of four members : the lowest is a group of thin-bedded sandstone and 
•olive-grey shale, the sandstone containing a perpendicular, bifurcating stem-like fossil, and also 



a true ScoUthus. This member is . . . . . . thin. 

The second is a massive quartzose conglomerate, of smooth ovoid pebbles, aboiit . . 10 feet. 
The third member is a thick mass of olive-grey shale and thin-bedded sandstone, probably the 

Tionesta Coal-measures, though of the aspect of the Vesj^ertine. It is about . . 175 „ 

The fourth, or uppermost, is a fossiliferous grey sandstone. Its thickness is 10 to . . 15 „ 



The Vespertine conglomerate caps the hills north-west of the Alleghany River. It is often mistaken 
for the Sei'al conglomerate and sandstone of the Coal-measures. 

Survey of fJie Formation. — It is apparent from the measurements here given, that the direc- 
tion of the maximum rate of diminution of this deposit is nearly due west. 

UMBEAL SERIES. 

The Umbral Series contains, in Pennsylvania, but one formation— the Umbral Red Shale. 
Though widely distributed, this is not coextensive with all the coal-fields, but thins out, as we 
shall see, under the bituminous coal region. Its prevailing character, which is that of a dark- 
brownish red shale and red sandstone, it steadily maintains throughout its range, except in Cam- 
bria and Somerset counties, where some greenish and blue calcareous shales or marls, and fossili- 
ferous limestone, intrude themselves in the mass, to become, further towards the S.W. and W., an 
important independent formation. The Umbral Eocks very generally occupy, in the anthracite 
region, the valleys between the ridges of Vespertine sandstone, and those of the Serai conglome- 
rate, or lowest coal-measures, and, in the bituminous coal region, the edges of the mountain 
table-lands between the same two formations. The following details will show a remarkable 
gradation in the thickness of this interesting deposit :— 

SOUTH-EAST Belt. 

Bordering the PoitsviUe Coal-hasm, the thickness of the formation on the Lehigh at Mauch Chunk is 
about ........ 3000 feet. 

At J/oim< Car6o?i, on the Schuylkill, it measm'es , . . • . 2950 „ 

Near the Susquehanna it is rather less than this. 
Middle Belt. 

Wyoming Basin. — Around the Lackawanna Valley, or north-eastern division of the Wyoming Basin, the type 
which the Umbral formation wears is that of a mixed group of shales and fine sandstones — the inferior portion 
containing red shale ; the middle, grey sandstones and butF slates ; and the upper, a very close-grained calcareous sand- 
stone, like hone. Near Scranton the red shale is extremely thin, and in some places entirely absent. From Scranton, 
south-westward, the relative proportion of this material augments, until, at Solomon's Gap, it greatly predominates in 
the mass, while the close sandstone of the middle and upper portions somewhat abates its thickness. 



UMBRAL SEEIES. 



145 



On the borders of the Lackawanna division of the basin, the average thickness of the whole formation is about 
350 feet j but in the Western or Nanticoke district, the whole is two or three times as bulky. 

At ColVs Gap the entire series measures ..... 440 feet. 

At Solomon's Gap its thickness is . . . . . . 569 „ 

kt Hert-og's Gap, north of Kingston, this JJmhral formation consists of olive-coloured and red shales, alter- 
nating with red and grey sandstones. The whole possesses a thickness, below the egg and nut-conglome- 
rate of the coal, of about ....... 3G0 feet. 

At Xanticoke, only the middle and upper portions are visible, the rest being concealed by the river. 
This visible part consists of soft calcareous red shale and sandstone, through a thickness of 260 
feet, surmounted by thin-bedded grey sandstone, in alternation with olive-coloured shales, 
capped by the hone-like beds. Total thickness visible, about . . . 400 „ 

At Broad Top Basin the Umbral limestone is a rather silicious, slightly foetid limestone, of a cloudy 
greenish white colour. 

In Trough Creek Valley it measures 3 to . . . . . . 4 „ 

\n Ground Hog Fa?^ey its thickness is . . . . . . 12 „ 

In Brush Creek Valley it is . . . . . . . 20 „ 

Third Belt. 

Near Astonville the Umbral series is composed largely, especially in its middle portion, of grey and 
greenish coarse sandstone, the thickness of which is . . . 350 feet. 

This is underlaid by red and greenish shales and ferruginous sandstones, with Lepido- 

dendron : thickness . . . . , . 87 „ 

And overlaid by a thin white conglomerate, . . . . 20 „ 

Sm-moun ted by blue, and a blue and red shale, about . . . .130,, 

Total thickness, . . 587 „ 

In the Hill at Cartersville, 1| miles from Ralston, the Umbral consists, in its lower part, 
of micaceous flaggy sandstone, in alternation with red and blue shales, in a thickness 
of about . . . . . . . . 300 „ 

Next a thin pebbly sandstone, and over this coarse white and greenish-grey sandstones, 
alternating with thinner beds of red and blue marly shale, nodular iron, as usual, 
occurring at the upper limit. Its thickness is about . . . 234 „ 

Total thickness, . . 534 „ 

At Ealston Olcl J/i nes the upper part only is seen. It is . . . 122 „ 

It consists of two soft marly shales, each between 40 and ■ . . . , 50 „ 

The lower red, the upper chiefly bluish and greenish, and between them argillaceous sand- 
stones, including a layer of balls of iron ore, . . . . 24 „ 

The upper shale two or three feet of nodular carbonate of iron. 

On Fall Creek, Towanda Basin, south side, the Umbral, as usual, in this region, is a triple 

group. Its lowest member is a soft red shale 1 8 to . . . 20 „ 

Its middle, a mass of yellowish fine-grained argillaceous sandstone, imbedding near its 
centre about 4 feet of ferruginous shale, with massive mottled grey concretionary 
iron ore — the whole . . . . . . 134 „ 

Its upper bed is a ferruginous bluish shale, containing a little red shale, . . 14 „ 

Total thickness, . . ' 1 G8 „ 

East of Tioga River the Umbral is very thin. 
Fourth Belt. 

Blosshurg. — Beneath this basin the Umbral series is a mixed group, composed of a large body of 
greenish grey sandstone throughout more than the lower half, and of red and green shales 
alternating with argillaceous sandstones in the upper part. The middle and upper portions 
contain several courses of nodular iron ore, consisting of carbonate of iron, with much extra- 
neous matter, and in some layers partially oolitic. The thickness is . . . 238 „ 
VOL. I. T 



U6 TYPES OF PALyEOZOIC 8TEATA. 

At the Conemaugh Gap, south-east base — Laurel Hill. — The Umbral series consists of red shale, including, 
near its base, beds of light-blue sandy limestone, and near its superior limit gi'ey and white argillaceous 
sandstone and iron ore. Its thickness is ..... 37U feet. 

On the Conemaugh Gap, at the Western Slope of Chestnut Ridge, the Umbral consists of the red 
marly shales, containing little grey sandstones in its upper half, centrally a thick bed 
of sandy limestone, and composed iu its lower part of olive shale. Its total thickness is . 15)5 „ 

It would seem not to be overlaid by any conglomerate, but is succeeded immediately by coal- 
measures. 
Fifth Belt. 

At Coudersport there is a gi-eeuish flaggy micaceous and argillaceous sandstone, including thin 
bands of red sandstone of similar composition. This rock, though possibly pertaining to the 
Vespertine series, is more probably the representative of the middle arenaceous member of 
the Umbral. It is overlaid by Umbral red shale, here very thin. The Umbral rocks appear 
to thin away altogether between Coudersport and Smethport. 

Smethport. — The Umbral appears not to extend so far westward. 

Survey of the Formation. — From the foregoing data, it would appear that this Middle Car- 
boniferous deposit thins faster towards the north, but changes to a calcareous type farther towards 
the south-west. 

SERAL SERIES. 

The Serai conglomerate, the only portion of the Coal formation whose changes of type and 
distribution admit of a general survey, exhibits the following modifications : — 

At Mauch Chunk its thickness is about . . . . . . 950 feet. 

It is here composed of hard grey silicious conglomerate in ponderous beds, coarse gi'ey sandstones, 

sandy clay -shales, and a few thin layers of fissile black coal, slate, and fire-clay. 
At Nesquehoning, on Rhume Run, its thickness is . . . . . 792 „ 

At Tamaqua its thickness is about . . . . . . 803 „ 

Here it is au alternation of very coarse silicious conglomerate in massive beds, the pebbles of the 
size of an egg or orange down to that of a nut or pea ; also of interposed coarse and fine grey 
sandstones, and here and there a sandy shale. There are also two or three thin imperfectly- 
developed beds of coal in it. 
At Potfsville its thickness is about . . . . . . 1030 „ 

Here the rock contains a less amount of coai'se conglomerate, a larger proportion of rough ai'gilla- 
ceous sandstone, two or three bands of coarse shale, two or three beds of coal slate, and a 
very thin, imperfectly-formed layer of very slaty coal. 
At Lorberry Gap, it is about ....... 675 „ 

Here the group consists of five or six thick strata of coarse egg and nut-conglomerate, forming as 
many bold ribs in the Sharp Mountain, with interposed beds of coarse sandstone and sandy 
shale. It embraces three thin impure seams of coal, and possibly a foiurth, with their coal 
slates. 

At Yellow Spring Gap — Dauphin — its thickness is about . . . . C60 „ 

It is a compact sandstone in the lower and middle portions ; an alternation of sandstone and con- " 

glomerate in the upper — the latter small in quantity. 
At Bear Gap, Wiconisco Basin, it measures . . . . . 460 „ 

At this locality, and indeed in the outcrops of the base of the Coal-measures throughout the west- 
ern part of the Wiconisco Basin, the group consists wholly of coal-measures, having lost 
entirely that preponderance of conglomerates and coarse sandstones which it contains 
throughout the Sharp Mountain, and indeed in both borders of the Potisville Basin as fiir 



SERAL SERIES. 



147 



west as Dauphin. It possesses here even less of the Sharp Mountain or conglomerate type than it 

exhibits in the Shamokin Basin still further north-westward. 
At Elingers Gap, Wiconisco Basin, there is an alternatipn of conglomerates, from pea to egg in coarseness, 

with fine and coarse sandstones, under a thickness of about . . . 230 feet. 

To this succeeds a group of four coal-beds, divided by pea, and pea and nut-conglomcratcs, and 

fine and pebbly sandstones, the whole possessing a thickness of . . . 400 ,, 

These two groups, in G30 feet of strata, represent the main lower group as it is developed at Bear 

Gap. 

Eastern Middle Coal-field, Hazleton and Beaver Meadow Plateau. — Here the conglomeritic group 
possesses a considerable thickness, tliough this is not susceptible of accurate determination. As 
seen at several points on the southern margin of the plateau, it is estimated to be not less in 
thickness than . . . . . . . . 700 „ 

Malianoy Basin, Ashland Gap. — In the gap of the Mahanoy Mountain at Ashland there is a great 
development of the conglomerate rocks. The pebbles are silicious, and of sizes ranging from 
pea to egg. Estimating its thickness from the top of the red shale to the lowermost coal-bed, 
it is not less than ...... . 600 „ 

If a ponderous bed of egg-conglomerate immediately overlying the bed of coal be included in our 

estimate, the total thickness will be . . . . . . 800 „ 

In Shamokin Gap.— In the Shamokin Mountain, at the village of that name, the lower or conglo- 
meritic group of coal-measures — restricting its limits, as we have done elsewhere, to the top of 
the hard rocks below the fifth seam of coal ascending, which is very generally the commence- 
ment of the softer coal-measures — consists of an alternation of ribs of nut, coarse conglome- 
rates, pebbly and fine-grained sandstones, with coarse shales and coal- slates in about equal 
proportions. It is made up of five of the hard silicious strata and four of the softer argilla- 
ceous, each of the latter including a bed of coal : some of these are of good quality and thick- 
ness. The whole group has here a thickness of .... 6.30 „ 

In Zerbes Gap, at Trcvorton, we see the most western natural section of the conglomeritic coal- 
measures in the Shamokin Basin. Here the group has a thickness of about . . 500 „ 

The mass consists of five ponderous strata of silicious conglomerate and coarse sandstone, and four 
thick beds of argillaceous shale and slate in regular alternation with them — the two kinds of 
rocks in about equal quantity. Each argillaceous member encloses a thick and valuable 
bed of semi-anthracite. In this western end of the Shamokin Basin these coals of the con- 
glomerate group are far thicker and of higher average purity than anywhere else in the 
corresponding part of the coal-measures around the anthracite region. 

In the Northern Anthracite, or Wyoming and Lackawanna Coal-fields, the formation consists of 
two strata, the lower chiefly a nut, coarse conglomerate of quartz and grey sandstone pebbles ; 
the upper a mass of dark-grey sandstones, sometimes pebbly. The average thickness of the 
lower stratum on the south-east side of the basin is 70 to 80 feet ; on the northwest side it 
is not more that 40 feet. The upper bed measures from 60 to 90 feet. 



At Scranfon the coarse lower rock is ... . 


80 feet. 


The upper fine-grained is . . . . . 


70 „ 


At Plane 7, Roaring Brook, CobVs Gap, the nut conglomerate is . 


45 „ 


The sandstone, . . . . . . 


45 „ 


At Solomons Gap, the lower is , 


80 „ 


The upper, ...... 


90 „ 


On the north side o f the valley, at Hertzog's Hollow, back of Kingston, — 




The upper rock is . 


60 „ 


The lower, ...... 


40 „ 



us 



TYPES OF PALiEOZOIC STRATA. 



In T roy Gap, back of Troy, the upper is 50 to . . . 60 feet. 

The lower, . . . . . . 50 „ 



At Warrior Path Gap, west of Solomon's Gap, the lower (conglomerate) is 75 
The upper (sandstone), ..... 60 



In the Hill at Cartersville, the Serai conglomerate consists of a pea conglomerate of 45 
And a pebbly sandstone, which is . . • • 15 >, 



110 feet. 



1.35 



At Nanticoke, Susquehanna Gap, the nut conglomerate is . . . .30 

North-West Belt. 

Near Astonville, the lower or true conglomeritic rock, consisting in part of sandstone, 

in part of pebbly rock, has a thickness of ... 45 feet. 

Upon it rests a coarse pebbly sandstone, which is . . . 25 „ 

But between them is a coaly and bituminous slate, of the thickness of . 2 „ 

72 



60 

At the Ralston Old Mines this interesting stratum has scarcely a thickness of 11 to . . 12 

The conglomerate itself is hardly . . . ■ . . 8 

In Broad Top Ilountain, near the Juniata River, the thickness of the Serai conglomerate is not 100 
Fourth Belt. 

At Blosshurg, the Serai conglomerate gi-oup consists of a very white sandstone, 

measuring ...... 20 feet. 

Surmounted by a pea conglomerate, which is . . . 7 „ 

27 



Survey of the Formation. — None of the land-derived or mechanically-formed sediments of the 
Appalachian Basin exhibit so remarkably regular a. gradation of declining thickness, or quantity 
of material in a definite direction, as this great sheet of gravelly matter underlpng and includ- 
ing the lowest coal-beds of the main or Serai coal series. It seems to thin faster towards the 
W.N.W., rapidly at first, but beyond the anthracite region very gradually. 



BOOK I. 

PEIMAL AND AUROEAL STRATA OF THE ATLANTIC SLOPE. 



In the South-eastern District, or Atlantic Slope, the only Palfeozoic formations are, as I have 
already indicated, those of the Primal and Anroral series, which I shall now proceed to describe, 
pursuing the general order adopted throughout this work — that is to say, commencing with the 
most southern hills, and passing through each tract from the N.E. to the S.W. 



DIVISION I. 

PRIMAL SERIES. 

INTRODUCTION. 

The three great divisions or formations of the Primal Series — the Primal Older Slate, Primal 
White Sandstone, and Primal Newer Slate, which appear within the limits of Pennsylvania, are not 
all present in each belt where the series is exposed. In the more south-eastern zones especially, the 
Primal Upper Slate, and in some localities the Primal White Sandstone, would seem not to have been 
originally developed, or to have been deposited interruptedly. Even where present, the distinct 
recognition of the slates is rendered, in many cases, very difficult, as already shown, from their 
close approximation, in aspect and composition, to the more ancient metamorphic schists. Some 
uncertainty must, therefore, remain in regard to the exact position of the lines of boundary 
between the two systems of strata in the more altered belts, that especially which is in contact 
with the southern Gneissic tract in Lancaster and York counties. It is obvious, from evidence 
already adduced, that the primal strata once overspread the southern Gneissic region much more 
extensively than they do at present, those portions only along the southern border having been 
preserved from the general denudation, which were protected by lying in the synclinal troughs 
of the more ancient rocks. 



CHAPTER I. 



PRIMAL SERIES.-THE SOUTHERN BELT. 

This southern outcrop of the Primal white sandstone has been already described, as it is trace- 
able from the vicinity of Trenton to that of the Schuylkill, along the northern side of the Gneissic 
belt. It was stated to occur in a closely-folded synclinal flexure, and to lap round the end of 
the altered Auroral limestone in the neighbourhood of Willowgrove, the southern and longer 
line extending through Barren Hill to the Schuylkill. This outcrop exhibits the stratum in a 
more thoroughly metamorphosed condition than it anywhere else presents. Though it has not 
lost the regular and parallel bedding distinctive of the formation, it has undergone an almost 
total alteration of its litliological aspect and character, bearing less resemblance to a fine- 
grained sandstone than to some varieties of quartzose felspathic gneiss. Its structure is 
decidedly crystalline, and we frequently recognise in it a large proportion of well-developed 
felspar, not however so entirely insulated from the quartz as in typical gneiss or granite. It 
would seem, indeed, to have experienced just that degree of semi-fusion requisite to develop an 
imperfect felspar, but insufficient thoroughly to melt the silicious sand which is in a measure 
diffused through the felspathic mass, without much influencing the crystalline condition of this 
latter, very much as the sand occurs in the Fontainbleau carbonate of lime. So gneissoid is the 
aspect of this rock, as it appears at Barren Hill and other localities, that it has generally been 
regarded by geologists and mineralogists as a true Primary rock, and has even been regarded as 
a variety of Eurite. It is traversed by innumerable joints, which divide it into small rhombic 
masses. In the Barren Hill range, as far indeed as the Delaware, the stratum in the main 
consists of thin-bedded altered sandstone, and, in the upper portion, much altered slate ; the 
Primal Newer Slate having a talcose and felspathic character. The massive thick-bedded more 
purely silicious part of the Primal white sandstone appears not to enter into the formation in 
this south-eastern belt, and hence the absence of the vitreous quartzose beds seen in other 
regions where that type of the rock has undergone the same extent of metamorphosis. It is an 
instructive fact connected with the change of constitution in this stratum, that it is in contact 
with very few trappean dykes or granitic veins of any land. Like many other instances of meta- 
morphosis on a large scale, it seems rather to have been caused by a general or diffused heat — 
most probably by the escape from within the crust, through innumerable joints and crevices, of a 
copious and perhaps often-repeated stream of intensely-heated volcanic gases and vapours. 
That we discover in this altered rock no traces of organic remains should not surprise us, since 
so few species of fossils have been as yet detected in the whole Primal series anywhere, even in 
those districts of the United States where the strata have been least affected by igneous agency. 

The disappearance of the narrow Primal zone at the Schuylkill, in its course towards the 
west, is probably the result of an actual thinning away of the formation, which throughout this 
line is of very limited dimensions. Upon the northern border of the limestone, the Primal white 
sandstone and Primal newer slate occupy the western and southern slopes of the North Valley 
Hill, the whole distance from Valley Creek, near the Schuylkill, to Back Township in Lancaster 



PRIMAL SERIES. 



151 



County, the lower beds of the sandstone being in contact with the gneiss which skirts it on the 
north. Between the point at w^hich the northern branch of the eastern belt disappears, about 
half a mile west of Willow Grove, and its reappearance at Valley Forge, it is nearly hid by the 
unconformable overlapping of the Mesozoic red sandstone, beneath which it is probably con- 
tinuous. Along the North Valley Hill, the sandstone contains a larger proportion than further 
eastward, of purely silicious beds ; it is even here much indurated and altered by heat, some of its 
layers containing minute needle-shaped crystals of hornblende, and a little crystallised talc, the 
evident products of segregation. The general dip of the strata is at an angle of about 70° to 
the south, identical w^ith that of the immediately overlying limestone. The Avhole mass may be 
distinctively recognised in the notches which give passage to both the East and West Branches of 
the Brandywine, and also at the pass by which the Philadelphia and Columbia Railroad turns 
northward from the valley towards Mine Hill. At some of these natural sections, the thickness 
of the sandstone disclosed is about 100 feet, and that of the overlying Primal newer slate 
perhaps a little greater. These rocks appear to have covered, at one time, nearly the whole of 
the northern Gneiss region of Chester County, for isolated hills of it occur in several localities. 

It is thus found in small outlying patches neq^r Valley Forge and between Downingtown and 
Mainesburg, and other places between the North Valley Hill and the Welsh Mountain. 

Between the township of Honeybrook and West Cain, commencing near the Lancaster turn- 
pike, above Werner's Mill, and extending westward nearly as far as the county line, there is a 
steep hill consisting of this formation. On the road from Downingtown to the Red Lion, in 
the lower part of Uvvclilan Township, the same rock occurs, in a small isolated hill running north- 
east and south-west for about a mile. We have already mentioned the occurrence of a similar 
detached hill of this sandstone near London Grove. Another, called the Buckingham Mountain, 
occurs near Centreville in Bucks County. 

RANGE OF THE SOUTHERN TROUGH OF PRIMAL ROCKS IN BUCKS AND 

MONTGOMERY COUNTIES. 

There exists a long, narrow, very straight, and closely-compressed trough of the Upper 
Primal Rocks, or the white sandstone, and the more slaty beds immediately beneath it, in a com- 
pressed synclinal flexure of the gneiss, extending the whole way from the Delaware below 
Trenton to the neighbourhood of the Wissahickon. The hardness of the Primal sandstone 
especially wdien highly altered by heat, as in the Belt before us, compared with the less 
cohesive Micaceous Gneiss, has caused this synclinal outcrop or trough to stand above the 
general plain of the country, especially of the district south of it, in the form of a low and very 
regular ridge. In Bucks, and even Montgomery County, this is very generally called " Edge 
Hill Ridge," under a mistaken but common impression that it is a prolongation of the hill 
bearing that name, which constitutes the southern boundary of the limestone basin E. of the 
Wissahickon. But this latter, as be seen by a glance at the Map, or a perusal of succeeding 
paragraphs, terminates near the Penny pack, a mile or more to the north of the belt now under 
description. The two ridges are, in fact, not connected except at their origin E. of the AVis- 
sahickon, where the anticlinal ridge of Barren Hill subdivides, by the intrusion into it from the 
E. of an anticlinal tongue of gneiss, sending forward its north-dipping outcrop in the sharp mono- 



152 



PKIMAL SERIES.— SOUTHERN BELT. 



clinal north-dipping Primal rocks flanking Edge Hill, and forming with this the compressed 
synclinal trongh of the long belt which we are tracing. From this point of divergence of the 
two ranges, which is about 2 miles E. of the Wissahickon, this belt of rocks, trending less toward 
the N. than the true Edge Hill, passes about one-fourth of a mile S. of Edge Hill village, and 
just S. of Mooretown, and. ranges tlience across the Penny pack near Walton's Mill. From 
this point it maintains its course E. about 16°. N., and runs on to Brownsville in Bucks County, 
this village being situated just at the southern base of the ridge. Crossing the Neshaminy at 
Mather's Mill, it passes S. of the village of Attleborough, the crest of the ridge, or probable synclinal 
axis, being just about one-half of a mile from the village. Thence it extends through Oxford, 
and a little N. of Fallsington, and reaches the west side of the Delaware River just below 
Morrisville, where its strata are well exposed in a quarry near the river-side. From this point 
it pursues the same straight course through the wide channel of the Delaware, in which it forms 
a ridge or ripple, and receding from the river-bank in New Jersey, loses itself from view under a 
covering of drift and sand. 

The general structure of this long and regular belt is everywhere very simple, being that of 
a nearly perpendicular synclinal fold, in which the strata of the two sides of the trough are 
compressed into approximate parallelism with each other, dipping at very steep angles, and in 
some places even in the same direction. An inversion of the southern side of the trough, 
though a frequent, is not an invariable feature, some of the sections across the ridge exhibiting 
these beds dipping steeply to the N. ; but in such cases, always at a higher angle than that at 
which those of the northern side of the axis dip southward. In other words, the axis plane is 
not perpendicular to the horizon, but invariably dips steeply to the S.S.E. 

The composition of this most southern of all our outcrops of the Primal strata is well seen 
on the road leading; into Attleborough from Bristol. Passing from the Gneiss at the southern foot 
of the Sandstone Eidge, the Primal strata present themselves under the following aspects and 
dimensions : — 

Section of Primal Sandstone S. of Attleborough. — Scale, 1 inch~lWQ feet. 

4Z!" 




Immediately succeeding the gneiss, there occur, on the southern slope of the ridge, a group 
of highly altered slates of the older Primal division. These are semi-crystalline, and contain 
much segregated felspar and mica. The group is between 200 and 300 feet thick. Over these, 
which may be seen in the trenches at the road-side, dipping very steeply towards the N., is the 
Primal white sandstone formation, which, as usual throughout this belt, indicates an extreme 
degree of metamorphism. The rock is very quartzose, and in some layers even semi- vitreous, 
and it contains mica, talc, and schorl in the thin partings which separate its beds. Surmounting 
these sandstone strata, or succeeding them in the centre of the ridge at the synclinal turn of the 
dip, are intercalated beds of white quartzose conglomerate, the pebbles generally not exceeding 
the size of a boy's marble. These hardest layers occupy the crest of the ridge. The visible 
thickness of the white sandstone from the slate on the one side, to the synclinal axis on the 



QUAERIES. 



153 



other, is about 300 feet, and tliis may be given as tlie approximate depth of the formation 
generally in its course through Bucks County. It becomes perceptibly thinner as it ranges 
westward towards the Wissahickon, for on the Limekiln Turnpike, S. of Edge Hill village, the 
whole formation, well exposed in a deep cut, shows a thickness not exceeding 150 feet. 

Owing to the amount of metamorphic action to which this belt of sandstone has been sub- 
jected, its strata possess a firmness of cohesion, and a tendency to lamination, which, combined 
with the original thinness and parallelism of its bedding, allow it to split up in quarrying into 
slabs or flagstones of unusual size, regularity, and strength. The rock is therefore extensively 
employed throughout the adjoining rural districts as a flagstone for steps, walks, and especially 
for dairies or milk-vaults. 

A prevailing structural feature throughout all this zone of altered Primal strata, is a system of 
cleavage planes, which dip invariably at a steep angle, 70° or 80" to the S.S.E., whether the 
strata themselves dip in that direction or not. This, be it observed, is the almost universal 
direction of the cleavage-dip throughout the Atlantic Slope. 

The following is a list of some of the principal quarries of flagging and building stone at 
present resorted to in this Ridge. None, it would seem, have been opened to the W. of the 
Pennypack, in consequence, apparently, of a reduction in the hardness of the rock, from abatement 
of metamorphic action in that direction. The two or three quarries E. of the Neshaminy, 
including that at Morrisville on the Delaware, are not here embraced. 

PEINCIPAL QUAERIES IN THE SOUTHEEN BELT OF PRIMAL SANDSTONE BETWEEN THE 

NESHAMINY AND THE PENNYPACK. 

1. Franklin Vansant's, near the Neshaminy, on the south side of the Ridge. This is a large quarry. 

2. Maiden Hicks's, three-fourths of a mile west of Vansant's, also on the south side of the Ridge. It contains a 
harder stone than that quarried by Vansant. The flags are thin and smooth. 

3. Mahltn Ridges quarry is situated 300 yards west of Hicks's quarry. It is a large one, yielding larger flags than 
any of the others. Stones can be procured measuring 6 feet by 8, and 4 by 6, and having a thickness frequently 
of from 2 to 6 inches. This quarry is half a mile east of Brownsville. 

4. Capt. E. Groom, Benj. Knight, and Mr Lerdom, all have quarries about half a mile west of Brown's Mills. 
All three yield a stone quite similar to that of Vansant's, of a yellowish white colour, and thicker flags than those 
from Hicks's, there being much good building-stone. 

5. Silas Rhoads and Samuel Acops have two quarries on the south side of the Ridge, near the Bustleton Turnpike. 
These quarries yield stone like those next east — a good building-stone, but a less proportion of large flagstone. 
The best building-stone is from the quarries of Groom, Knight, and Lerdom. 

There are no other quarries opened in Bucks County to the westward. All the flagging-stone produced is 
immediately bought up. It sells at the quarry for $1 per horse-load. The building-stone is sold at about 12| cents 
per perch. The best descrij^tion of building- stone at the quarry costs 20 cents per perch. 



GENERAL GEOGRAPHICAL LIMITS OF THE PRIMAL STRATA WEST OF THE SCHUYLKILL, 
AND SOUTH OF THE CHESTER COUNTY LIMESTONE VALLEY. 

In describing the geographical distribution of the older Primal Slates south of the Chester 
County Valley and west of the Schuylkill, no difficulty presents itself in defining their Northern 
limit, which coincides very nearly with the Northern base of the South Valley Hill, or, in other 
words, with the Southern margin of the limestone of the valley, the interposed Primal white sand- 
stone being, as already mentioned, very thin. Nor is there any obscurity in the boundary between 
VOL, I, TJ 



154 



PRIMAL STRATA OF MONTGOMERY. 



this slate belt and the gneissic rocks to the south of it from the Schuylkill to the Brandjrwine, this 
line having been already defined as that of the Northern edge of the gneiss. But to the west- 
ward of the Brandywine a difficulty does present itself, from the introduction of a number of 
troughs included between the series of narrow tapering anticlinal belts, or fringes of gneiss, by 
which the Primal series is spread prodigiously to the southward, almost to the Southern line of 
the State. If the actual limit between the lowest Primal rocks and the gneiss could be minutely 
followed, it would be found to wind in and out, in a zigzag manner, between the uplifted spurs of 
gneiss, each successive trough to the S. lying somewhat further towards the W. than the 
preceding one. The general line of boundary is represented on the Geological Map ; it is 
designedly somewhat vague. Looking at the entire area occupied by these Primal rocks, between 
the Schuylkill and the Susquehanna, and between the Pecquea and Conestoga valleys and the 
Maryland State line, we are reminded of the form of a hatchet or cleaver, the long slender belt 
between the Schuylkill and the Western Branch of the Brandywine representing the handle, and 
the wide slate district of the South-western townships of Chester, and of the Southern ones 
of Lancaster, representing the blade. 

The Southern limit of the Primal slates within the State is the Northern ed^e of the lone 
tract of Serpentine, under the State line in Lancaster ; but other narrow ranges occur in Mary- 
land, before we reach the main district of gneiss. Progressively expanding in its range south- 
westward, the belt of older Primal rocks is even broader in York County than it is in Chester 
and Lancaster ; and in Maryland it is wider still. 

COMPOSITION OF THE PRIMAL STRATA AS THEY ARE DEVELOPED IN THE MONTGOMERY 
COUNTY VALLEY, EAST OF THE SCHUYLKILL RIVER. 

It is only on their Northern outcrop, or that extending eastward from the Wissahickon 
towards the Pennypack Creek, that we find the Primal rocks wearing a resemblance to their 
ordinary sedimentary aspect, undisguised by metamorphism. There the principal mass is an 
alternation of thin beds of bluish grey sandstone and still thinner layers of brownish sandy 
slate, very much the type which the older Primal rocks exhibit on the Susquehanna above 
Columbia. A partial metamorphism is observable, however, even in this Northern outcrop, for 
the most argillaceous, or slaty partings, present oftentimes the aspect of an incipient talcose 
crystallisation. 

Along the Southern border of the Limestone Valley, all the Primal rocks wear a greatly 
more altered character ; the lower beds, or those adjoining the gneiss, presenting indeed so 
advanced a condition of crystallisation as to be entitled to the name of Semi-Porphyroidal 
Rocks. On a first inspection, especially of the weathered and disintegrated outcropping frag- 
ments of these lowest Primal beds, the observer is very liable to confound the formation with 
the uppermost hornblendic felspathic layers of the adjacent genuine gneiss ; and until my own 
researches enabled me carefully to study and trace the several strata of this zone, the propriety 
of referring these porphyroidal beds to any system of rocks newer than the Gneissic formation, 
was never, I believe, entertained. 

In the district of the Schuylkill and Wissahickon, the three members, of which the Primal 
series there consists, present the following aspects and dimensions. 



PRIMAL ROCKS ON THE SCHUYLKILL. 



155 



The lowest, or semi-porphyroidal group, evidently an altered sandy slate, or argillaceous 
sandstone, is remarkable for the regular parallelism of its lamination and bedding ; the laminse, 
alternately light and dark, being exceedingly thin, many of them usually packing within the thick- 
ness of an inch. These laminae consist, where the rock wears its most metamorphosed form, of 
white earthy, imperfectly-developed felspar, and perfectly- developed earthy hornblende. Besides 
these alternate whitish and dark streaks, the cross fracture of the rock displays a multitude of 
ovoidal concretionary crystallisations, generally only specks in size, but sometimes of the dimen- 
sions of bullets, the larger and better formed concretions being frequently genuine crystals of 
felspar. In some of the layers certain laminae are studded with isolated crystallisations of 
hornblende. 

The maximum thickness of this group at the Schuylkill is about 300 feet ; but not more 
than 100 feet can be seen immediately at Spring Mill. 

The next rock ascending, or the second member of the Primal series, is a species of imper- 
fectly-formed talcose and micaceous slate. When most metamorphosed, it consists of wavy, 
nearly parallel laminae of quartz, mica, and apparently some talc, with innumerable crystals of 
dodecahedral garnet. It exhibits this composition near the mouth of the ravine of Aramink 
Creek, opposite Conshohocken. The twisted or wavy form of the plates of mica seems due, as in 
the coarse mica-slates of the true gneissic series, to the interference of the garnets and of the 
segregated quartz. When less altered, tliese strata have the characters of an impure sandstone, 
pervaded with particles of imperfectly-developed mica and talc. This rock is very liable to 
disintegrate from exposure to weather ; it decomposes into an unctuous talcose earth, of a mottled 
deep-red and blue colour, forming a highly ferruginous soil, a chief source from whence the 
percolating waters extracting the oxide of iron have formed those large deposits of brown 
hsematitic iron-ore that adjoin the outcrops of the Primal and lower Auroral formations. The 
very abundant fragments of white quartz, resembling a pale chert, which strew the surface near 
the outcrop of this second member of the Primal series, are not fragments of genuine injected 
quartz veins penetrating the strata, but merely large segregations of the quartzose matter of 
this rock consequent upon its alteration by heat. Such plates of fine-grained cherty quartz, 
sometimes including imperfectly-developed felspar, may readily be mistaken at first glance for 
the more quartzose felspathic layers of the altered Primal white sandstone of the range of 
Barren Hill. The apparent thickness of this middle member of the Primal series is here about 
200 feet. 

The third and terminating rock of the Primal series near the Schuylkill is the white sandstone 
above mentioned, so conspicuously exposed in the anticlinal ridge of Barren Hill. It is a thin- 
bedded, yellowish white, very compact rock, presenting in composition much imperfectly- 
developed felspar, and showing a tendency to a rhoniboliedral fracture. The more solid layers 
seldom exceed two inches in thickness. Other more schistose bands, consisting of the same 
quartzose felspathic matter in intimate fusion, contain likewise many minute partings of crystal- 
line mica and talc, and the surfaces of the more solid felspathic beds exhibit very frequently at 
these partings innumerable minute crystalHne specks of pure black schorl. This rock possesses 
a thickness in Edge Hill, Barren Hill, and near the Wissahickon, of 35 to 40 feet ; but further 
eastward the group is far more massive, being, in the vicinity of Willow Grove, not less probably 
than 100 feet thick, and in Bucks County, in the southern trough, not less than 300 feet. 



156 



PRIMAL ROCKS 



LOCALITIES WHEEE THE PRIMAL ROCKS MAY BE BEST STUDIED. 

On tlie Southern side of the basin, tlie lowest, or semi-jyorjyhyroidal group, is well exposed for observation in the 
ravine of the Aramiuk, and thence at the base of the river-hills eastward to the Ferry House opposite Spring ^lill ; 

again in the point of the hill at Spring Mill, just North 
Fig. 9.— Section on Ajamink Creek. of the William Penn Iron-Furuace. It has been laid open 

to view by quarrying, at the entrance of the Wissahickon 
into the gueissic hills, and again at the foot of Chestnut 



70" , >• ,ve'^*'LvO^'°it»*' ^' Hill, on the Gerrcautown and Perkiomen Turnpike. It is 

T«u:!u»u-2Mfi. ^^v"- ^ ' n^ niaterial very well adapted for macadamising the turnpike 

roads, being tough and durable, while it is easily quai-ried. 
The Second Division of the Primal Series, or the Mica-Talcose Group, is best exposed along its Southern outcrop, at 
and near the mouth of the Aramink Creek. Elsewhere upon this line it is generally covered by surface matter. 
Its fragments are abundant in the soil upon it. Ranging as it does immediately at the foot of the Gneiss Hills, it is 
very genei-ally concealed by the rubbish of the rocks higher on the slopes behind it. 

The same obscurity attends this southern outcrop of the upper Primal rock — the White Sandstone ; but a fair 
exposure of this exists in the vicinity of Spring Mill, immediately on the road at the base of the Furnace Hill, where 
a large and old excavation for iron ore has revealed the stratum and its steep Northern dip. But the best exposures of 
the Primal white altered sandstone are at the several cuts through the Barren Hill ridge, formed for the passage of the 
turnpike roads. Perhaps the completest of all is at Edge Hill village, where the whole formation is finely developed 
in a deep cut on the northern Pennsylvania or Water-Gap Railroad. Some of the upper beds of this rock are beau- 
tifully developed in an excavation on the South side of the anticlinal of Barren Hill, adjacent to the village of Spring 
Mill. It may be well seen, under the modifications induced in it by cleavage, in the end of the Church Hill at White- 
marsh. 

Along the Northern side of the basin, the lower group.s, in their unaltered aspect of sandy slates and argillaceous 
sandstones, are best beheld near Sandy Run, especially in the deep cut in that vicinity for the Northern Pennsylvania 
Railroad. Further to the eastward the Primal white sandstone sheets the Southern slope of the same Northern 
boundary of the valley, and is fairly exposed on two or three of the cross-roads of the country. 



COMPOSITION OF THE PRIMAL STRATA IN THEIR DISTRIBUTION WEST OF THE 

SCHUYLKILL. 

When the Primal rocks W. of the Schuylkill and S. of the edge of the red sandstone, 
are carefully studied, they exhibit as remarkable a constancy in the characters of the white 
sandstone member, as they present aberration in the litliological t}'pe of the other or slaty 
groups. 

Primal Wliite Sandstone. — The sandstone retains throuo-hout its entire distance to the 
Susquehanna, almost identically, the features which distinguish it in Montgomery County. It 
presents, that is to say, in those outcrops where it has undergone the greatest amount of meta- 
morphism, a semi-vitreous texture, specks of imperfectly-developed felspar, partings delicately 
coated with white talc, and surfaces imbedding minute segregated crystals of schorl. In its less 
altered belts, especially those north of the Chester County Valley, as the north Valley Hill and 
the Welsh Mountains, the sandstone is ordinarily less firmly cemented, and therefore more 
extensively crumbled and eroded along its outcrops, more porous and softer, and less divisible into 
thin flags ; it contains, moreover, but little segregated talc or schorl. 

Pinmal Slates. — But when we trace the slates of the Primal series, in our progress to the W. 
or S.W., we find that they are not so persistent in their characters, but put on some new and 



WEST OF THE SCHUYLKILL. 



157 



interesting features, losing others wliicli are distinctive of the group to the eastward of the 
Schuylkill. Thus the peculiar speckled and semi-porphyroidal group of beds, at the very base of 
the whole Primal series, in contact with the gneiss at the Schuylkill, is less distinctly recognised 
as we follow the boundary between the two systems of rocks westward for a few miles. We 
may still detect it, though more obscurely, S. of the Paoli ; but we cannot recognise it when 
we reach the Brandywine. This change may be due either to the running out of this division of 
the formation by loss of material, or it may result from a change in the conditions of meta- 
morphism arising either from a modification in the original composition of the stratum, or from a 
more intense and prolonged exertion of subterranean heat. The form of rock which replaces the 
dark semi-porphyroidal beds at the base of the Primal series, and therefore of the whole vast 
Palaeozoic system, is one which well deserves to be critically studied and noted. It is a variety 
of silicious, talco-micaceous slate. In certain districts W. of the Brandywine, especially towards 
the Susquehanna, where the metamorphic action seems to have been in its highest energy, the 
crystalline character of these rocks is at its maximum, and it is there sometimes difficult to dis- 
tinguish the strata from certain forms of the more micaceous beds of the true Gneissic or Hypozoic 
system. An extensive comparison, however, of the materials of the two formations, enables one 
almost invariably to determine definitely between the real micaceous slate and that which only 
simulates it. 

It is impossible to subdivide into its several component members the Great Lower Primal 
Group of Southern Pennsylvania, W. of the Schuylkill Eiver, for the more we study it in detail, 
the more nugatory become our eflForts to trace the separate strata or determine their strati- 
graphical relations. This difficulty proceeds from several causes : first, a pervading transverse 
cleavage, which extensively efi"aces all clear traces of the original bedding ; secondly, the presence 
of innumerable plications, often so closely compressed as to appear as only one uniform dip, the 
anticlinal and synclinal foldings in many cases escaping detection through the obscuring influ- 
ence of the cleavage ; and, thirdly, mutations in the composition, or at least in the now prevailing 
crystalline or metamorphic constitution of the beds. 

Defining, then, the entire succession of slaty rocks embraced between the upper limit of the 
genuine Gneiss and the bottom of the Primal white sandstone, as one natural group, it will be 
best represented as an alternation of talcoid silicious slate, talco-micaceous slate, and quartzose 
micaceous rock, usually also schistose, or thinly laminated. Along the Northern side of the tract 
occupied by these older Primal rocks— that is to say, adjoining the great limestone of the valley 
on the south — the principal form which the stratum assumes is that of a talcoid slate,full of lenticular 
lumps of granular quartz, apparently the silicious material in excess, in a state of segregation. 
This form of the fragments prevails especially where the cleavage, always dipping to the S.E., is 
not coincident with the bedding. In the rarer instances where these two sets of planes do concur, 
the lamination is more parallel, and the silicious granules more dispersed among the talc. 
Alternating with the talcose slates are beds of the more micaceous variety ; but the more highly 
micaceous, silicious schists, prevail chiefly in the lower half of the formation, or, as respects the 
belt in question, in its central and southern portions. 

Besides the talcose and the micaceous varieties of the metamorphosed Primal slates, there 
exists a third species of rock under the form of a nearly pure clay-slate of the character of roofing 
slate. This seems to occupy a horizon comparatively low in the series, for it is never inter- 



158 



PRIMAL STRATA OF MONTGOMERY. 



stratified with tlie talcose or upper division, but with the highly-crystalhne micaceous rocks, 
which seem to prevail most in the central and lower. 

DESCEIPTION OF THE SECTION ALONG THE BEANDYWINE. 

(See engraved Section.) 

A careful examinatiou of the Section along the Brandywine Creek " will render more evident than any general 
description can, the conditions under -which the older Primal slates appear, as respects their crystallisation, cleavage, 
and dip, witliin this middle portion of the Southern Primal Belt in Pennsylvania. 

Restricting our attention to the portions of the section south of the Chester or Downingtown Valley, it will be 
observed that talc-slate, with a steep northward dip of 80°, and au equally steep South-dipping cleavage, immediately 
succeeds the limestone a few hundred feet south of the railway station. From this point to the road leading to West 
Chester, about a thousand yards below the Bridge at Taylor's Ford, we have a succession of talc-slates and talco- 
micaceous slates, more or less quartzose, dipping for the most part southward, and full of South-dipping cleavage — with, 
however, occasional steep North dips, implying the presence of acutely-folded flexures. In one instance the cleavage 
also dips towards the north. This whole belt manifestly belongs to the older Primal slates. Between Taylor's Ford 
and Brinton's Run, or the vicinity of Chadd's Ford, the section crosses a complex belt, embracing much micaceous and 
hornblendic gneiss, with soft felspathic gneiss, under various conditions of dip, and irregularly alternating with mica- 
ceous and talcose slates, occasionally containing garnets. This alternation of the hardei-, more massive gneiss, with the 
softer, more loosely aggregated, and, to appearance, less perfectly developed, seems to mark the presence of two systems 
of rocks, an older or Hypozoic gneiss, and a more modern or Azoic series, probably the lower Primal slates in conditions 
of extreme metamorphism. I conceive that the most natural interpretation of the geological features of this district will 
be found in the hypothesis of a succession of narrow parallel anticlinal folds of the older gneiss, enclosing between 
them folded troughs of the newer metamorphic gi'ouj), precisely as we recognise a similar series of anticlinal fingers and 
synclinal basins of the two respective formations in the region of the East and Middle Branches of the "Whiteclay 
Creek further to the S.W. Grasping the whole of this part of Chester County in one general survey, I suppose it to 
contain a series of closely-compressed anticlinal and synclinal flexures — the anticlinal lifting the older rocks, the syn- 
clinal holding within them the newer, and disposed in echelon, or in oblique order; the more southern, as a general rule, 
terminating further to the west than the more northern. This conception satisfactorily explains the presence of the 
numerous parallel synclinal valleys of the still higher Auroral limestone, with their bounding outcrops of the Primal 
white sandstone, dipping conformably with the semi-gneissic or micaceous schists. It likewise accounts for the rapid 
horizontal expansion of the whole slaty Azoic region, from the Brandy wine westward. 

THE PRIMAL STRATA, AS EMBRACED IN THE SYNCLINAL VALLEY OF MONTGOMERY 

AND CHESTER COUNTIES. 

These rocks lying in a trough of the great Gneiss formation, but unconformably upon its more 
contorted beds, consist of all the three older Primal strata which this part of Pennsylvania pos- 
sesses, together with the chief part of the Auroral or magnesian limestone series. The Primal 
rocks form the border of the valley, the South side of which they fringe with a continuous belt, 
while they skirt the Northern side more interruptedly, ranging from the Eastern point of the 
trough, near the county line of Bucks and Montgomery, to the Wissahickon ; and again, from 
Valley Forge continuously westward through Chester and Lancaster counties, the interruption in 
the region of the Schuylkill being by an unconformable overlap of the Southern edge of the 
Middle secondary red shale or Mesozoic red shale and sandstone. In the district E. of the 
Schuylkill, the Southern fringing belt ranges along the base of the Gneissic hills to beyond the 
Wissahickon ; but from thence eastward they occupy a narrow ridge of their own, called Edge 
Hill. The Northern outcrop forms, from the Eastern head of the valley westward to the Wissa- 



EASTERN END OF BASIN. 



159 



liickon, tlie bounding ridge of this portion of the limestone valley. All the Eastern end of the 
trough, from a point about half a mile W. of the Willow Grove Turnpike, to near the Hunt- 
ingdon Turnpike E. of Pennypack Creek, is underlaid by the Southern belt of the Primal 
rocks, the Auroral limestone terminating at J. C. Tyson's, E. of the source of Sandy Run, a 
mile to the S.W. of Willow Grove. 

STEUCTURE OF THE EASTERN END OF THE LIMESTONE BASIN OF MONTGOMERY 
AND CHESTER, FROM THE WISSAHICKON TO THE PENNYPACK. 

Some interesting features exhibit themselves in the structure of our great Southern limestone- 
basin towards its Eastern termination. Its most Eastern division, extending from the Wissahickon 
to the Pennypack, is regularly bounded by a Southern and a Northern ridge or belt of hard Primal 
rocks ; but these ridges do not coalesce, as woidd be the case if the basin was one of the most 
simple synclinal form, but they run on separately past the termination of the limestone in two 
independent and slightly-approaching crests, till they terminate about a mile apart in the vicinity 
of the Pennypack, the outcrops of the Primal strata being prolonged indeed across that stream 
nearly to the Huntingdon Turnpike. The whole trough ends in the form of a swallow's tail with 
the two prongs collapsed, as when the bird is darting. The included bed of limestone itself forks, 
but not into points as acute as those presented by the belts of Primal strata which confine it. One 
prong of the limestone valley prolongs itself eastward to within half a mile of Willow Grove, 
past the source of Sandy Run ; while the other more Southern one, following the Northern base of 
Edge Hill, extends almost to the Willow Grove Turnpike. This forking of the end of the whole 
basin is the consequence of a complex anticlinal flexure of all the strata of the region prolonged 
from the eastward, across the Pennypack, between the two Primal spurs, and dying down in the 
eastern end of the trough of limestone. Its effect is to form two subordinate independent 
troughs in the eastern end of the one general basin, as exhibited on the Geological Map. Willow 
Grove is situated in the Northern synclinal valley on the Primal sandstone ; while the Southern 
trough crosses the turnpike about half a mile S., the upper rocks at the crossing being the 
same white-sandstone group. Between these two branch basins of the Primal series, we find in 
reality a double and not a single anticlinal axis ; or in other words, the wave is concave on its 
crest. This is evident from the existence of two separate anticlinal belts or points of the gueissic 
rocks penetrating westward between the spurs of sandstone in the vicinity of the road con- 
necting Blaker's Store and Morgan's Mill. These two anticlinal points of the gneiss enclose a 
synclinal ridge of the Primal rocks, the highest or capping stratum being the conglomeritic bed 
which terminates the white-sandstone group. Advancing westward as the two anticlinals sub- 
side, we discern at the turnpike only one broad flat arching of the upper Primal slates, lifted to 
the surface by the more southern and important of the two flexures. It is this line of elevation 
apparently which causes the broad swell of upper Primal sandstone, in which the limestone 
valley abruptly ends at HoUowell's and Tyson's farms. The more northern and feebler axis 
does not show itself in the topography to the westward of Willow Grove. 

The extreme synclinal point or last visible trace of the more southern basin of Primal strata, 
or that of the true Edge Hill, is at the Huntingdon Turnpike near the Sorrel Horse Inn ; and the 
further exposure of the northern or Camp Hill belt, or trough, is on the same meridian, or road 



160 



PRIMAL STRATA OF MONTGOMERY. 



leading N.W. from the Sorrel Horse Inn. About half a mile to the eastward of this road, this 
belt of the Primal rocks is overlaid by the southern conglomeritic margin of the Middle secondary- 
red sandstone ; but the belt itself very probably terminates near this point. 

The following sections display the changing structure of the Primal belt in its progress 
Westward. 



Mesozoie Red ScUt^ 



Fig. 10.— Section E. of Pennypack at Sorrel Horse Ian. 
(Scale, 1 inch = 2000 /eei.) 



Crantle A 



Mesraoic Ued Snndat 



Fig. 11.— Section from Morpfan's Mill to 
the west of Yerke's Factory. 
(Scale, 1 inch = 600 /eei.) 




Fig. 12.— Section of Primal rocks at Will( 
Grove Turnpike. 
{Scale, 1 inch= 1500 feet.) 




Sd4l. P'- 0- Salu "s^i 



Fig. 13.— Section at Forking of Basin, near Tyson, 
west of Willow Grove. ' 
(Scale, 1 inch = 2000 /t'e<.) 




DETAILS RESPECTING THE PRIMAL ROCKS IN THE DISTRICT OF WILLOW GROVE. 

On the AVillow Grove Turnpike near Willow Grove, we may discern the strncture of the whole Primal Zone as it is 
represented in our section. Just north of the forking of the Turnpike, we detect on the sides of both the roads 
the Primal rocks, leaning at a moderate angle upon the gneiss, dipping towards the little valley in which Willow Grove 
is situated. Crossing this valley to the road leading to Newtown, and ascending tlie hill forming the southern boun- 
dary of the same small valley, we find this hill sheeted over with the Primal sandstone, dipping to the opposite quarter, 
or to the north, and forming tlius with the other outcrop the Northern Branch Basin. Here, upon the northern 
slope and end of this hill, the fragments of the sandstone contain numerous vestiges of Scolithus linearis, the fossil char- 
acteristic of the White Primal Sandstone. If now we advance along the turnpike southward, we may readily perceive 
the synclinal structure of tlie southern valley, or that at the northern foot of Edge Hill, by noting fii-st the southward 
gentle dip of the upper layers of the Primal slates by the roadside, and presently a similar dip in the overlying white 
sandstones at the brow of the hill as we descend into the valley. Crossing the. valley and the crest of its southern 
ridge, or Edge Hill, we may plainly see the same Primal rocks recur in the inverse order under an opposite and steeper 
dip to the northward. 

Farther eastward the relative positions of the several belts of strata are disclosed to careful study in the line 
of our section, crossing the whole belt from Morgan's Mill to Yerke's Mill or Factory. At Morgan's Mill we find the 
lowest layers of the Middle Secondary Red Sandstone, under their usual condition of a very coarse conglomerate. 
A few hundred feet southward from Morgan's Mill on the road to Willow Grove, we have the gneiss emerging from 
beneath this margin of conglomerate ; while across a meadow south-eastward, and by the road to Blaker's Store, 
we detect the northern synclinal belt or trough of the Primal sandstone dipping gently southward near Newport's 



BARREN HILL. 



161 



house, and beyond this, on the road near his gate, dipping very steeply northward, constituting a narrow trough. If 
we advance south-eastward along this road, we will detect a second belt of the gneiss occupying a breadth of several 
hundred yards, until, near the intersection of this road with that leading to Shelmire's Mill, we encounter the eastern 
point of a synclinal hill of the Primal sandstones. Near this intersection of roads is a second anticlinal axis, which, 
between the Pennypack and this point, lifts to the surface the older Gneissic rock, but which here, and to the west- 
ward, only elevates the overresting Primal slates. At this part of our section, where it crosses the road running from 
Edge Hill to Shelmire's Mill we come upon the conglomerate beds which in this neighbourhood terminate the Primal 
series. These cap the synclinal hill ali-eady mentioned, and likewise the two spurs to the south of it, which are only the 
two outcrops of the hard Primal rocks that here form the Southern or Edge Hill basin. Both these latter ridges are 
abruptly cut down at their eastern ends by transverse erosion, the point of the basin of upper hard Primal rocks being 
here nipped off. 

Tracing the noi-thern synclinal line of the Primal rocks eastward from near Morgan's Mill, we follow it through a 
hill lying eastward of Newport's house, and detect it at several points till it crosses the Pennypack, and leads along the 
northern brow of a ridge half-a-mile to the north-west of the Sorrel Horse Inn. In this ridge we may detect the lower 
or slaty Primal rocks in a highly metamorphic condition, approximating in their aspect and crystalline condition to a 
rather finely-laminated gneiss, with some beds of which they are in contact. In the centre of a close synclinal fold of 
these slates the white Primal sandstone is seen densely cemented and very vitreous, and only about twenty feet in 
thickness, all the upper beds having been cut away. In this synclinal fold the strata dip about 60° to S. As already 
mentioned, the red sandstone conceals the termination of the strip of Primal at a short distance beyond this spot to the 
east, or before it reaches the county line of Bucks and Montgomery. 



PRIMAL STRATA WITHIN THE AURORAL LIMESTONE VALLEY OF MONTGOMERY AND 

CHESTER COUNTIES. 

First Anticlinal lifting the Primal Rochs. — Besides the Northern and Southern fringing out- 
crops, and a long contracting Eastern belt, in which the trough terminates, there occur two or 
three anticlinal uplifts of the Primal rocks within the outer limits of the limestone of the valley. 
The most southern of these insulated tracts is the narrow belt of Barren Hill, a prolongation of 
Edge Hill, which range is but a monoclinal outcrop of the Primal white sandstone and its under- 
lying slates lifted into a perpendicular dip by an anticlinal flexure in the gneiss immediately 
behind it to the S. The axis of this anticlinal wave is prolonged all the way to the Schuyl- 
kill, gradually subsiding westward till it permits the ujDper Primal white rocks to bury them- 
selves near Spring Mill under the overlying Magnesian limestone. It is a closely-compressed or 
sharp anticlinal, elevating the gneissic rocks to the surface as far westward along the sinking 
crest of the Edge Hill ridge as the vicinity of Heydrick's Mill, on the road leading from the 
Bethlehem Turnpike towards Willow Grove. Westward of this point of depression in the ridge, 
no gneiss is visible in its axis, but only the uppermost layers of the older Primal slates, which 
are here more or less talcoid from metamorphosis by heat. Even these talcoid layers sink out 
of view before we reach the village of Barren Hill, from a point E. of which, to the village of 
Spring Mill, the only rock exposed along the summit and flanks of the ridge is the ivhite 
Primal sandstone in a highly felspathic condition, with talcose 

° ^ Fig. 14.— Section at Middleton's. 

partings. ..^i*'*'" 

A section of this compressed flexure is exposed in a cut on 
the turnpike road at Middleton's. It is interesting as showing 
a bending of the outcrops of the strata both ways down-hill, 
from the pressure of retreating waters. ^' 

Barren Hill presents us with some striking examples of overturned outcrops, from the mere 

VOL. I, X 




1G2 



PEIMAL STRATA OF MONTGOI^IERY. 



Fig. 15. — Overtm-neJ outcrop of Primal Sandstone in a quarry 
in Barren Hill, on the Kidge Road. 

Jn--— ■ 




effect of the pressure induced by the denuding waters during their diffused rapid subsidence 
at the time the kind was uplifted. It is both there and in many other parts of Pennsylvania 
on far too great a scale to be attributable to the softening action of rain and hill-side pressure. 

Between this anticlinal of the Primal rocks 
and the base of the Gneissic hills to the south, 
there lies a narrow parallel trough full of exqui- 
sitely-beautiful local scenery, its soil a deep 
covering of fertile earth derived from the Gneissic 
and Primal strata. This little synclinal vaUey 
appears to contain here and there patches of the 
lower beds of the Auroral magnesian limestone; 
but the outcrops of this rock are difficult to 
detect in the earthy covering above mentioned ; 
and it is more than probable that the trough is too shallow to contain any long continuous 
belt of it. The limestone is detected resting on the Primal white sandstone, in a south 
dip close by the Toll Gate on the Wissahickon and Perkiomen Turnpike at Middleton's. 

Second Anticlinal of Primal Mocks. — The next anticlinal belt of insulated Primal rocks within 
the Limestone Valley east of the Schuylkill Eiver, is a long narrow range of the Primal older 
slates in a more or less talcoid condition, which, commencing at this river at Conshohocken, and 
extending eastward, contracts, and finally subsides at the Perkiomen turnpike south of Marble Hall. 
This uplift of the Primal strata through the Magnesian limestone is simply a prolongation of the 
bold anticlinal fold of the lower rocks of Bethel Hill, west of the Schuylkill, opposite Conshohocken. 
It evidently originates in the plateau of gneiss to the westward. Sinking to the eastward across 
the Schuylkill, it insulates a trough of the Magnesian limestone between it and the belt of 
the gneissic hills bounding the river between Conshohocken and Spring Mill ; and beyond the 
Western head or termination of this limestone basin, insulates between the gneiss which the 
anticlinal there uplifts, and the main Southern gneiss, a similar contracting trough of the Primal 
slates. It is along this trough of the slates that the upper part of the Gulf Creek flows, until it 
breaches the anticlinal, and passes northward through the deep gorge called " The Gulf " The 
axis, or back of the wave, is probably prolonged to the eastward across the Wissahickon, for 
apparently a couple of miles beyond the Perkiomen Turnpike, near which the talcose slates seem to 
sink under the limestone. Even on the Bethlehem Turnpike a ridge in the limestone, directly in the 
prolongation of this axis, betrays in its structure and soil the j)resence of this anticlinal wave. 

It is worthy of remark, that aU the marble of the limestone basin of Montgomery County is 
confined to the synclinal trough adjoining the anticlinal axis now described, upon the N. ; the 
genuine marble not extending more than half a mile from the uplifted belt of slate, nor eastward 
in its line of strike beyond the neighbourhood of the point of sinking down of the Primal slates, 
or past the Meridian, where the anticlinal rapidly loses its force. As the marble is evidently 
only a highly metamorphic variety of the ordinary Magnesian limestone, crystallised and 
changed in tint by igneous action from within the earth, it is quite natural that it should run 
thus parallel with and adjacent to this line of uplift, produced as this has been by the protruding- 
forces of the interior. The whole of this belt of marble is in fact but the vertically upturned, and 
occasionally inverted, Northern side of this anticlinal wave, the side along which the maximum 



t 



ANTICLINALS. 1G3 

amount of igneous influence is invariably manifested. In offering this explanation of the origin 
of the marble by metamorphism, it is proper to observe that we must not ascril^e the whole of 
the change to its proximity to the line of anticlinal uplift of the Conshohocken axis. There is 
a tendency in the u-hole of the limestone of the Southern half of the general valley to a much 
greater degree of alteration than belongs to the same rocks in the Northern half. Throughout 
this entire synclinal belt the metamorphism from heat, of course, has been far greater along its 
Southern than upon its Northern margin, partly because the strata of the former side are nearer 
the principal injections of igneous rocks of the whole region, and partly in consequence of the 
perpendicular or even inverted position which has permitted the subterranean volcanic vapours 
to per\"ade them more freely, and exert their maximum influence. 

Analogous with this general tendency to a higher degree of metamorphism along this South side 
of the basin, we have the efiect of the powerful anticlinal uplift of the Bethel Hill axis, causing 
a similar greater change along the narrow belt immediately adjoining it on the N., where the 
limestone is likewise in the condition of marble. 

Third Anticlinal of Primal RocJcs. — A short and relatively insignificant flexure of the strata 
ranges near the northern margin of the Limestone Valley, and throws up a ridge of the Primal 
rocks from a little N. of Frea's Corner, where it is encroached upon by the edge of the red sand- 
stone, to the point S. of Eeuben Cox's Limekilns. Near the Western end of this ridge the rocks 
composing it are well exposed in two or three small quarries ; while a road leading a certain 
distance along its summit enables us to detect the Primal white sandstone capping the talcose 
slate quite near its crest. The Primal rocks are exposed in this ridge through a length of a little 
more than one mile. On its Northern flank the white sandstone appears to be inverted, or to dip 
Southward. Between the North base of the ridse and the next or fourth anticlinal, there runs a 
narrow trough of the Magnesian limestone, about one-third of a mile broad. This at its Western 
end is shut under by the overlapping edge of the red sandstone, which here crosses the limestone 
obliquely from near the Western end of this third to the Western point of the fourth anticlinal 
of Primal rocks. In this trough the limestone is quarried near the road leading N. from Frea's 
Corner, and again more extensively at the limekilns at Reuben Cox's. 

Fourth Anticlinal of Primal Rochs. — A fourth and comparatively feeble anticlinal flexure lifts 
the Primal rocks to the surface through the limestone of the valley in the Church Ridge, crossing 
the Wissahickon Creek near the village of Whitemarsh. East of the Wissahickon this axis at 
the Bethlehem Turnpike exposes only the uppermost of the Primal rocks, or the white sandstone. 
On the south side of the anticlinal axis line, or fold, these strata dip at a moderate angle to the 
southward. On the North side they dip perpendicularly, making this a flexure of the true 
normal form. The Episcopal Church at Whitemarsh crowns the summit of this regular anti- 
clinal ridge. In the exposure at the Turnpike, the altered sandstone is pervaded with cleavage- 
planes, dipping according to the prevailing law of cleavage-structure throughout all Southern 
Pennsylvania, at a rather high angle to the S. Near the very axis of the flexure the dip of 
the cleavage-joints is towards the axis plane, or steeply to the N., making, with the South- 
dipping cleavage of the beds N. of the axis, that fan-lihe arrangement of these fissures 
which is so characteristic of anticlinal folds in strata highly susceptible of cleavage-structm-e. 
(See the Section.) 

To the Westward of the Wissahickon this anticlinal belt of the Primal rocks is prolonged 



164) 



JUNCTION OF PRIMAL AND AURORAL STRATA. 



into a ridge considerably higher and longer than that crossed by the Turnpike at the Church, 
extending for about three miles ; it terminates in a low point near the extension of the 
Plymouth road. It is flanked, and is even saddled for much of its length, by the white Primal 

Fig. 16. — Section along the Bethlehem Turnpike from Sandy Run to Chestnut Hill. 




sandstone. The Primal slates, somewhat talcose, but in a less metamorphic condition than on 
the Southern side of the valley, emerge to the day in several places along the crest of the ridge. 
They are much affected, as usual, by cleavage ; and though the anticlinal structure of this long 
narrow hill is obvious, no exposures permit us to detect the actual place of the turn of the dip 
westward of the turnpike at the Wissahickon. 

A trough of limestone — ^that, namely, in which Hains's Inn is situated — is embraced between 
this axis of the Church Hill and the Fort Washington Ridge, or northern general boundary of 
the valley ; but though doubtless prolonged far to the westward of the Wissahickon, this rock 
soon vanishes from view, being buried under the margin of the Middle secondary red sandstone. 
That overlapping stratum extends obliquely across the trough from the Wissahickon opposite 
Fort Washington to the Northern base of the anticlinal ridge of the Primal rocks, meeting this 
about half a mile west of that stream, and there bringing the accessible limestone to a point. 



PASSAGE FROM THE PRIMAL TO THE AURORAL STRATA AT SPRING MILL AND 
CONSHOHOCKEN, ON THE SOUTH SIDE OF THE LIMESTONE BASIN. 

DESCRIPTION OP SECTION PAST SPRING MILL ACROSS THE SOUTHERN SIDE OF THE LIMESTONE BASIN OF 
MONTGOMERY, BEING A CONTINUATION OF THE SECTION ALONG THE SCHUYLKILL FROM PHILADELPHIA TO 
SPRING MILL. 

The accompanying Section is intended to illustrate the relations of the Primal strata at the 
Schuylkill to the Gneissic rocks beneath them, and to the Auroral limestone overlying them. 

Fig. 17. — Section of the Primal and Gneissic Strata, and of the Auroral Limestone and its Ore-Ground, near Spring Mill. 




It commences on the point of the Furnace Hill, just east of the William Penn Furnace, at the northern or upper 
limit of the gneiss. Here the passage from the harder gneiss to the softer porphyroidal talcoid slates is marked bv 
a decided change to a gentler slope on the flank of the hill. A portion only of the lower Primal rock is seen in 
the point of the hill as it stretches towards the Schuylkill. From the position of the outcrop of Primal sandstone 
at Lentz's old ore-digging, it may be inferred that the section crosses the same outcrop nearly at the road at the 
base of the hill. There is a blank of about 400 feet between this road and the base of the Barren Hill Ridge, but 
this blank occupied by the surface materials of the little valley is evidently underlaid by the Primal strata, no 
Auroral limestone having ever been detected here in wells or excavations. The section now crosses the ridge near a 



MATSAN'S EUN. 



165 



quarry of the upper beds of Primal white sandstone, which here dips to the S. at an angle of 35". Just north of the 
crown of this narrow ridge, the same white rock has been recognised in sundry wells sunk in quest of ore, dipping 
perpendicularly, or even turned under to a S. dip of 85°, proving that the anticlinal axis of the ridge lies between 
these wells and the quarry before mentioned on its south slope. 

In immediate contact with these perpendicularly-dipping beds of Primal sandstone occur steeply-inclined beds of 
dusky ferruginous magnesian limestone pervaded with cracks, giving the rock a brecciated aspect. At this junction 
of the Primal and Auroral strata is the southern limit of the deep deposits of ferruginous clay and loam which 
imbed the large accumulations of brown hsematitic iron-ore, which constitutes already such a prominent source of 
wealth to the whole southern half of this great limestone belt. Our section crosses about 50 feet of recognisable 
outcrop of the Auroral limestone, seen sometimes in the deeper ore-diggings, sometimes in the valley of Spring Mill 
Brook. Wherever exposed, these limestone beds dip a little to the south of the perpendicular. Beyond the limit here 
stated no rock is exposed for about 400 feet, until we approach the road leading from Spring Mill to Marble Hall ; but 
in that vicinity we detect steeply -dipping talcoid slates, elevated by the anticlinal axis further north. Our section now 
crosses the talcoid Primal slates on the south side of this anticlinal for about 600 feet. These slates dip like the 
limestone at a very steep angle to the south. Here on the northern side of the summit of this ridge, which is the pro- 
longation of Bethel Hill of Conshohocken, our section encounters the large trap-dyke which extends from the south 
slope of Bethel Hill through the village of Conshohocken and the crest of this slate ridge past the point we are upon 
to the Pei'kiomen Turnpike, which it crosses between Marble Hall and Barren Hill. This dyke is here about 30 feet 
in width. Northward from the trap-dyke we pass over in the line of section between 500 and 600 feet more of talcoid 
slates, till we approach the northern foot of the hill, where we detect the lower upturned beds of the Magnesian lime- 
stone. At the base of the hill we come upon the blue and shaded marble ; and here the marble belt is between one- 
third and one-half of a mile broad. 

Our section displays a wide trough or deposit of ore-ground between the two anticlinal uplifts which it intersects. 
This ore-ground beginning on the south just north of the summit of the "White Sandstone Ridge, reaches to the foot of the 
higher ridge of Primal talcoid slate. Neither on the White Sandstone Ridge nor the Talcoid Slate Hill is there any 
depth of ferruginous soil sufficient to include a notable amount of iron ore ; but in the trough between them, the ore, 
containing loam and clay, rests in a very deep deposit, measuring in some longitudinal gutters not less probably than 
100 feet. It is in these deeper collections of the ferruginous earth that the largest deposits of the richest ore should 
be obtained. The iron contained in this ore-bearing soil has been in part derived from the lower beds of the Magnesian 
limestone, some of the strata of which are excessively ferruginous ; but in larger part it has proceeded, no doubt, from 
the disintegrated talcose slate, a rock abounding in iron, as the red colour and composition of its clays demonstrate. 

The line of our section crosses another narrower belt of ore at the foot of the Furnace Hills. This deposit pertains 
to a deep lodgment of ferruginous earth and decomposing slate-rock, just at the contact of the talcoid slates and the 
Primal White Sandstone. The ore is for the most part more sandy than that which overlies the limestone and talcoid 
slates further removed from the Primal white sandstone. 



PASSAGE BEDS AT THE MOUTH OF MATSAN'S RUN OPPOSITE CONSHOHOCKEN. 



Fig. 18. — Section at Caldwell's Furnace. 



A transverse section at Cddwell's Furnace, from the Primal Slates into the Auroral Limestone, displays, — 

1 . Talc-slate on the north slope of the bounding ridge, dipping 

perpendicularly. 

2. North of the slate, a narrow band of mottled blue-and- 

white crystalline limestone and marble. 

3. A bed of talcoid or nacreous altered slate, apparently 

about 100 feet thick. 

4. A band of impure altered limestone, about 50 feet thick. ^' 

This passes under the southern edge of the Engine House. 

5. A talcoid and garnetiferous altered slate, extending to within 100 feet of the brook. This underlies the Furnace. 

6. The lower beds of the Auroral magnesian limestone, as a continuous mass, visible on both sides of Matsan's 

Run and in its channel. 




1G6 



PRIMAL KOCKS WEST OF SCHUYLKILL. 



Ou the north side of Matsau's Run, or about 200 feet south of the Conshohocken bridge, there is a good exposure 
of the lower beds of the Auroral magnesian limestone near the railroad ; here the rock is sub-crystalline, and mottled 
whitish and blue ; it weathers of a ferruginous yellow, and dips without contortion 77° to N. 25° W. 

The alternating or passage beds, above described, range westward up the valley of Matsan's Eun, on its south side 
nearly to its head, some of the limestone bauds having been quarried to furnish a flux for the Furnace. 

THE PRIMAL WHITE SANDSTONE BOUNDING THE CHESTER COUNTY YALLEY 

WEST OF THE SCHUYLKILL. 

Having defined tlie outcrops of the Primal white sandstone bordering the main basin of 
limestone of Montgomery County, and traced them to their terminations E. of Willow Grove, 
and having shown the several narrow anticlinal belts in which they appear within this basin, 
we will now follow them along l^oth margins of the same great trough, as it stretches in a nearly 
straight line through Chester into Lancaster County. 

THE SOUTHERN OUTCROP OF THE PRIMAL SANDSTONE. 

It is an interesting fact disclosed in the attempt to trace continuously the Primal white 
sandstone along the Southern side of the Chester County Valley, that it ceases almost entirely 
on this border of the basin in the neighbourhood of Spring Mill, or E. of the Schuylkill, and 
that no efibrt to discover it in a regular outcrop of any length or appreciable thickness has yet 
disclosed it on the West side of the river, or even for several miles westward, until we reach 
points opposite the Spread Eagle and the Paoli. North of the latter place the outcrop of this 
sandstone may be recognised at two or three spots just at the base of the South Valley Hill ; in 
some instances by the character of the soil, and the angular fragments of the sandstone imbedded 
in it ; and in one case in a house-well at the country-seat of Mr Thomas Biddle. In these spots 
the thickness of the whole stratum cannot exceed a very few feet, nor can we suppose it con- 
tinuous ; for if it were, we should almost certainly detect it in the numerous lanes, and in the 
railroad cuts, which so abundantly intersect this border of the basin. 

The next point further westward at which we recognise unequivocally the outcrop of this 
interesting rock is on the South Eoad, about one and a half miles E. of Downingtown, or one- 
third of a mile W. of the Eailroad Viaduct. Here the rock is exposed in the gutter of the road, 
and it has been dug into in a well near by. A soft sandy material, the decomposed stratum, is 
yet distinctly discernible at the spot. It presents its ordinary, somewhat talcose, aspect. The 
dip of the strata, both here and generally along this margin of the valley, is very nearly vertical. 
We cannot discover any vestiges of the formation, either S. of Downingtown or for a few miles 
W.S.W. of it, though it is very probable that it aj^pears and disappears in the same obscure 
manner as it does further eastward ; but in the vicinity of Coatesville, and westward of that 
village, this well-marked rock possesses a sufficient thickness to project conspicuously in rugged 
outcrop at the entrances of the numerous ravines and gorges which there cut the South bound- 
ary of the valley. Even there, however, it seems not to possess a thickness of more than 30 or 
40 feet, and is sometimes thinner ; and yet, from the superior hardness of its semi-vitreous 
mass, and its silicious nature making it invulnerable to the chemical influences of the elements, 
it is a very prominent feature in the stratification, even where thus thinly developed. The rock 



SERPENTINE. 



167 



in nearly perpendicular clip thus holds its course to the westward, skirting the border of the 
valley until the limestone itself terminates, and the two sides of the basin ultimately unite. 
This union of the two lines of the Primal sandstone occurs near the Conewango Creek in Drumore 
Township ; yet the long and remarkably straight synclinal trough within which they lie stretches 
on in precisely the same course for a few miles towards M'^Call's Ferry ; but before reaching the 
Susquehanna River the synclinal structure ceases, and a monoclinal South dip alone remains. 
Only the lower Primal rocks, or the micaceous crystalline slates, reach the river. Indeed, it is 
doubtful if the sandstone extends even to the Conewango. 

In another Chapter it is shown that other outcrops of the Primal white sandstone occur 
some miles to the S. of this long line, and entirely insulated from it, proving that the forma- 
tion has at one time spread itself very extensively to the southward. 

BELTS AND LOCALITIES OF SERPENTINE SOUTH OF THE LIMESTONE VALLEY OF MONT- 

GOMEEY AND CHESTER COUNTIES. 

1. The Serpentine and Steatite Range of the Schuylkill in the Southern Edc/e of Montgomery County. — This, the most 
eastern zone of the magnesian rocks in Southern Pennsylvania, lies entirely within the middle or micaceous belt of 
gneiss, or highly metamorphic Azoic rocks, but near its northern border. It is a long and straight line of outcrop of 
steatite or serpentine, extending from the northern brow of Chestnut Hill between the two turnpikes, across the Wissa- 
hickon Creek and the Schuylkill to near the Baptist Meeting-house Road, about a mile west of Merion Square. Along 
the eastern and central parts of its course, the southern side of this belt consists chiefly of a talcose steatite. The 
northern side, containing much serpentine in lumps, dispersed through the steatite ; but towards the western side this 
separation seems to disappear. The serpentine division, or band, is conspicuous on the line leading from Chestnut 
Hill down to Thorpe's Mill, where enormous blocks, without any distinct traces of stratification, cover the surface 
along the line of the bed or dyke. The same rock is similarly exposed on the west side of the Wissahickou, opposite 
Thorpe's Mill, and thence westward along the north side of a laue leading up to the Eidge Road. The whole belt is 
vaguely exhibited at the summit-level of the land between the Wissahickou and Schuylkill valleys ; but, descending 
towards the Schuylkill, we again discern, on the north side of the line of outcrop, the huge blocks of mingled serpentine 
and steatite, until, near the Schuylkill river, they choke the bed of the ravine next north of the Soap-stone Quarry. On 
the west side of the Schuylkill, this serpentine and steatite rock is still visible in large blocks, a little above the soap- 
stone of that bank of the river ; but between this point and the vicinity of Merion Square, the rock, though discernible 
at a few points, is nowhere conspicuous. About one-third of a mile west of Merion Square, it is quite prominent 
again, the surface being strewn with huge masses. It may be distinguished at once from any other mineral aggregate 
of the region, not merely by the enormous dimensions of its loose blocks, but by its rugged, frowning, dark aspect, and 
also by the general coating of dark lichens and other cryptogamous plants. The serpentine seems not to follow the 
steatite the whole distance to the western termination of the belt. 

Only in a few neighbourhoods does the steatite, constituting generally, as already said, the southern half of the tract, 
present itself in sufficient purity and mass to be profitably quarried. On the east bank of the Schuylkill, however, 
about two miles below Spring Mill, at the spot called the Soapstone Quarry, it has long been successfully wrought ; 
and on the west side of the river, in one place on the bank, and at another about one-third of a mile west, the rock 
has been quarried, thovigh upon a less extensive scale. In former years it was excavated to a small extent on the 
west bank of the Wissahickou, just opposite Thorpe's Mill ; but the band of steatite at this place appears to be too thin 
to warrant its being pursued at present. 

Both at the Wissahickou and the Schuylkill, the steatite, which is regularly stratified, dips steeply to the N. 35" W., 
agreeing in its inclination with the subjacent beds of mica-slate ; but on the west side of the Schuylkill, at the 
points where it has been exposed in quarries, it dips at a more moderate angle to the south-east, thus indicating a pro- 
bably synclinal structure in this central portion of the belt. The material is used chiefly for the lining of stoves, fire- 
places, and furnaces. The principal market for it is the city of Philadelphia. 

Towards the end of the last century and the beginning of this, before the introduction of the marble of Montgomery 



168 



BELTS OF SERPENTINE. 



County for street-door steps in Philadelphia, this easily-dressed stone was in some demand for that use ; but it proved 
badly adapted to the purpose, because of the very imequal hardness of its different constituent parts, there being a 
diflSiculfy in getting blocks free from knotty lumps of imperfectly-crystallised serpentine, which make it to wear 
unevenly under the attrition of the feet. We may sometimes see, in an old and much-worn door-sill of this rock, these 
knots of the serpentine mineral projecting above the steatite like hob-nails in a plank. 

2. Second Outcrop of Serpentine- in our progress westward. — The next outcrop of the serpentine in our progress west- 
ward, occurs on the western brow of the table-land of Gneiss just south of the narrow limestone trough of the upper 
part of Gulf Creek. It is within half a mile of Morgan's Corner. The exposure there has a length of only a few 
hundred feet, but it is at least 300 feet wide. It is bounded on the south by genuine gneiss, and immediately on its 
north by talcose and steatite slate. Between this belt and the narrow strip of limestone in the valley north of it, there 
is an uplift of hornblendic gneiss, distant from the serpentine about 100 yards. Immediately north of this last outcrop 
of the gneiss we encounter a repetition of the talcose-slate formation, or older Primal rocks under that highly altered 
gneissoid aspect which they wear so conspicuously on the Schuylkill between the Aramink and Spring Mill. 

The belt of serpentine comprises both true injected or igneous serpentine, and serpentinous steatitic talc-slate. In the 
two quarries in Avhich it is best exposed, sti-atification is visible in some places, but in others there is none. In a quany 
east of the road, the dip is steeply northward, while in that on the opposite side of the road it is 70° southward. 



Fig. 19.— Section of South Vulluy Hill, east of Morgan's Comer. 




3. TJiird Belt of Serpentine, or that of the neighbourhood of the Faoli. — "We come next in order to the most extensive 
serpentine range of Chester County. This has its eastern extremity on the iavm of General Wayne, of Revolutionary 
memory, about one mile south-east of the Paoli Hotel, and just at the line of East Town and Willistown. Its western 
termination is near the western line of East Goshen, and about two and a half miles N.N.E. of West Chester. These 
limits give a total length of about six miles. Its coin-se is W. about 25° S., coincident nearly with that of the 
strike of the gneiss and talcose slate which border it for the greater part of its length. Commencing in a narrow 
point of the General Wayne farm, it widens i-apidly as we trace it westward, until, at a distance of a mile at and 
beyond Maris's Grist Mill, its total breadth is nearly 2000 feet. In this central part of its course it runs for nearly 
three miles almost parallel with the old State Road to AVest Chester, at an average distance of one-third of a 
mile, gradually approaching the road until it crosses it about four miles from the Paoli, or three-fourths of a mile north-east 
of East Goshen Friends' Meeting-house. It is here reduced to a breadth of no more than 400 or 500 feet. Under this 
average width it ranges on, passing the Barren Hill School-house and aci'oss Ridley Creek, and thence for one mile 
further to its termination beyond the old blacksmith's shop at John Gheen's farm. Throughout its entire range, this 
serpentine appears chiefly as a stratified rock, and in its widest central portion we may distinctly perceive that it has 
a synclinal or \mdulated structure. It is, indeed, rather an impure talcose slate, largely impregnated with serpen- 
tinous matter, than a zone of genuine intrusive serpentine. Dykes of this mineral it does, however, embrace, and these 
on a small scale are very numerous, but they bear in the aggregate a small proportion to the whole belt. Its stratified 
structure is well exposed at the crossing of the State road, where it dips 70° N. ; also in the ravines which cut it 
near the Barren Hill School-liouse, and still more convincingly near the old smithy at John Gheen's, in which latter 
locality it has a nearly perpendicular dip, but discloses under close inspection innumerable minute contortions and 
plications of the thin laminae of the rock. 

The eastern end of this zone of serpentine is bordered both sotith and north by the talcose-slate formation, in which 
it seems to lie as a folded synclinal trough ; but from the vicinity of Maris's Grist Mill to its western termination, 
its southern margin is in contact with a massive hornblendic gneiss, its northern touching in some places upon ordinary 
talcose slate, but in others, especially towards the western end, upon quartzose and garnetiferous micaceous gneissoid 
rock, of the group I have called Azoic. This garnetiferous micaceous guiess may be seen dipping steeply northward, 
conformably with it, close to John Gheen's dwelling. The prevailing dip of the hornblende gneiss, bounding it on the 
south is northward 70° — 80°. 



WEST CHESTER BARRENS. 



169 



Along the northern edge, or a little outside of the northern margin of this line of serpentine, trap-rock occurs in 
greater or less abundance, and apparently as a succession of narrow elongated dykes. These seem not to be strictly 
parallel with the serpentine and other strata, but to observe a more North-east and South-west direction. Narrow dykes 
of this rock intersect, indeed, this range of Serpentine Barrens in many neighbourhoods, and this is a feature which 
may be noticed in nearly all the outcrops of serpentine within the State. 

The crystalline minerals of this tract, few in number, will be mentioned in a future Chapter in connection with 
those of the other serpentine belts. 

4. FouHh Tract of Serpentiiie. — There is a small and apparently insulated development of serpentine about three- 
fourths of a mile S., 45° W., from the old smithy near Gheen's dwelling. It is evidently not in the prolongation of the 
long belt just described, but is almost exactly in the range of the Serpentine Barrens, one mile north of West Chester, 
with which it is possibly united, though no external indications of such connection present themselves, there being an 
interval of half a mile between the small patch and the eastern extremity of the Main West Chester Line of Barrens. 
Though small, this area of serpentine is readily discerned, forming a little elliptical mound. 

5. Fifth Serpentine Tract, or that of the West Chester Barrens. — In the same general line with the long range of 
serpentine traversing Willistown and East Goshen, though strictly about one-third of a mile further S.E. than its line 
of strike, is the Serpentine belt of the West Chester Barrens. The N.E. point of this appears to be just S.W. 
of the East Branch of Chester Creek, or one-fourth of a mile N.E. of the West Chester Railroad. It crosses the 
railroad nearly two miles from the centre of West Chester, exposing imperfectly its stratified structure in the railroad 
cuts ; whence it ranges about one mile further between the forks of Taylor's J^un. The mean width of this belt is at 
least 1000 feet. Though chiefly an impure and stratified serpentinous talcose slate, the tract includes many injections 
of genuine igneous serpentine. 

Like all the middle ' and western portions of the Paoli belt, this tract is bordered on the South by massive 
hornblendic gneiss, while it is fringed on the North by the earlier talcose slate and micaceous slate of the South Valley 
Hill, into which it appears somewhat abruptly to graduate. 

The more compact varieties of this serpentine have been \tsed for building-stone in West Chester and its vicinity, 
and the material proved to be well adapted for many architectural uses. It has a very pleasing effect when newly 
built into walls, as it has a quiet tone of greyish green ; but exposure to the elements for a few seasons causes it to 
fade, or to become more dull and greyish. Several neat structures have been built of it. 

The chief minerals of this range hitherto discovered are mentioned in the general list already referred to. 

6. Sixth Serpentine Outcrop. — To the S.W. of the Main West Chester Belt of serpentine, there occurs near 
Hoope's Saw Mill a small outcrop of serpentine and steatite, which is evidently in the same line of strike with the 
large serpentine tract north of West Chester, and the small detached one to the east of that. 

7. Seventh Outcrop. — Another trivial exposure of Magnesian rock, chiefly steatite, occurs on Taylor's Run, on 
the land of Caleb Cob, close to an outcrop of granular limestone. These are about half a mile S.W. of the 
previoiLsly-mentioued locality of serpentine. 

8. A still more trivial locality of steatite is at the Black Horse Tavern, on the road to Taylor's Ford. It is in the 
same general line with the three previously-mentioned localities of magnesian rocks. 

9. Again, on the same line, both serpentine and steatite present themselves about three-fourths of a mile S.W. 
of the Brandywine, on the farm of Mr Wurth. 

All the above six exposures of serpentine and steatite occur so nearly in one line, and this is so probably a line 
of dislocation connected with the synclinal fold of the older strata, that we can hardly doubt that these outcrops 
derive their existence from one chain of injections of true serpentine mineral along the southern margin of the talcose 
Primal slates. 

10. An entirely insulated exposure of associated steatite and serpentine occurs near Marshall's Mill, on the West 
Branch of the Brandywine, on the farm of Humphreys Marshall. This does not seem to be connected with any of the 
other serpentine injections of the district, for it is too far South to be in line with the six outcrops previously described, 
and too far North to be related to the large serpentine ridge east of Unionville. It is more strictly in bearing with a 
small exposure of the same rock, which occurs in the neighbourhood of West Marlborough Inn. 

11. The last-mentioned locality. West Marlborough Inn, possesses a small exposure of stratified serpentinous rock, 
containing injections of serpentine; and this is the most Western of all the outbm-sts of this rock until we come to the 
great one, which commences at the Little Elk Creek and extends for many miles to the Susquehanna River, which it 
crosses. 

VOL. I. Y 



170 



BELTS OF SERPENTINE. 



12. There succeeds now a more Southern line of insulated exposures of serpentine, the most Eastern of which is 
encountered half a mile S.E. of the Willistown Inn, in Willistown Township. This includes both serpentine and 
steatite. 

1 3. The nest locality of the serpentine rock of this belt is near Darlington's Comer, and here occur carbonate of 
magnesia and crystalline chlorite, besides the interesting mica mineral Kliuoclore. 

ft. Near Strode's Mill, in East Bradford Township, there occurs a large outburst of serpentine, with lithomarge 
and fine talc connected with it. 

15. Another exposure of the same magnesian rock exhibits itself N.W. of Strode's Mill, near the Prospect Hill 
Academy. This is nearly in a line with a large belt of the same rock east of UniouYille. 

1 G. One or two detached knolls of serpentine occur in Lower Oxford Township, the furthest west of the small 
insulated patches known to us. 

17. Serpentine Belt of tlie Unionville Barrens in Newlin Township. — We have arrived now in our progress towards 
the S.W. at a conspicuous belt of serpentine, about equal in magnitude to that north of West Chester, and one of 
the most interesting of the whole series for the crystalline minerals which it contains. It lies in the south-eastern 
corner of Newlin Township, about one mile N.N.E. of the village of Unionville. It has a mean breadth of some 
800 feet or more, and its total length is about one mile. It lies altogether within the micaceous talcose slate, 
many portions of which rock wear here a very quartzose and sandy aspect. This belt consists of stratified ser- 
pentinous talcose slates, with much injected or infused true igneous serpentine. It is intersected by several narrow 
dykes of fine-grained basaltic trap, which trend N.E. and S.W. Besides these, there occur some interesting mineral 
veins. One of these, which has attracted the notice of mineralogists, is a narrow vein of very hard white albite, 
including many crystals of corundum, some portions of the vein being indeed almost an emery or corundum rock. 
An attempt was made some years ago by a skilful and most zealous mineralogist of Chester Coimty, D. Lewis 
Williams, to mine regularly this very hard and intractable but valuable material ; but the undertaking was not long 
persevered in. Loose chunks or blocks of the corundum rock strewing in one place the north slope of the ridge of 
serpentine, derived either from the above-mentioned vein or from other injections, were collected at one time to the 
amount, it is said, of between six and seven tons, and exported to Europe. 

Besides the albite with corundum, there occur several veins or dykes of granite, consisting almost exclusively of 
felspar. This mineral is here in such purity, indeed, as to be in much request for the purposes of dentistry. Owing 
to the demand for felspar entirely free from extraneous associations, a successful quarry has been opened, and has 
already furnished a considerable quantity for the market. Associated with the pure orthoclase, which is in very 
large crystals, there is also occasionally much oligoclase or soda spodumene, another felspar mineral. 

There are several other insulated small localities of serpentine west of the Brandywine, but they are not of 
sufficient importance to be entitled to a special description. 

Long Serpentine Belt of the State Line on the Southern Edge of Chester and Lancaster Counties. — A very extensive 
belt of stratified and injected serpentine rocks ranges near the State Line from the Little Elk Creek in Chester 
County across the Octorara Creek to Maryland, and thence across the Susquehanna. Its length from the Little 
Elk to the Susquehanna exceeds 17 miles, and the tract is prolonged beyond the river through the northern 
edge of Maryland for several miles further. Its mean width may be given at about one mile. This is a range of 
wild and stony barrens scarcely tilled, except in a few spots on its two margins, and overgrown with stunted black 
oaks, and other trees characteristic of the magnesian soils of all these serpentine belts. Along its southern border 
this magnesian formation is in contact with black hornblendic gneiss, but apparently without conformity of dip. On 
the Susquehanna a different rock, a micaceous talcose slate, boimds it on the S. ; along it northern edge it is every- 
where bordered by the micaceous talcose slate of the Primal series ; and this latter formation seems to lap round its 
eastern extremity, near the valley of Little Elk Eiver. Much trap-rock presents itself just west of the Little Elk 
along the southern edge of this range of serpentine, and dykes of that material occur within and adjacent to the belt, 
especially throughout its southern half, and apparently along its whole course. One of these may be seen on the 
main road leading to Carter's Ferry at the crossing of Buck Kxm. 

The zone of serpentine rocks now before us is especially remarkable for containing large quantities of chromiferous 
iron-ore. It is indeed one of the chief sources of chromate of iron in the United States, having already furnished large 
supplies of this mineral for both the home and the European demand. The chrome ore penetrating the serpentine rocks 
in true lodes or veins, with more or less regularity, has likewise been met with in great abundance in a fragmentary 



IKON OEES. 



171 



state upon the surface of the barrens, and to a small depth amid the disintegrated materials of the serpentine. It has, 
therefore, been mined both by regular mine-shafts, and by superficial pits or holes, and trenches. The scattered surface 
ore, locally called " Sand Chrome," has been extensively gathered from the beds of the ravines and valleys which 
intersect the barrens, and after being washed on the spot has been shipped away to market. When, for a succession 
of years after the first development of this mineral, the high price of $45 per ton stimulated the discovery and pre- 
paration of it, many thousand tons of the stream or " sand chrome " were transported to the sea-board, especially 
to Baltimore. More lately, since the richer deposits of the more accessible surface ore have been in chief part 
exhausted, resort has been had to mining in some of the more regular solid veins. Only two such subterranean 
excavations are now, however, systematically prosecuted, owing partly to the circumstance, that the present market 
for the minei'al is easily glutted, and partly to the fact, that nearly all the most promising localities of the region 
are at present monopolised by one individual. Both of these mines are situated a little westward of the 
East Branch of the Octorara Creek. It will suffice to present here the chief features of one of them, namely, 
Wood's Chrome Mine. This is situated not far from the Horse-shoe Ford of the Octorara, the vein of chromi- 
ferous iron-ore observing a nearly N.E. and S.W. direction, and dipping 45° to N.W., or with the local slope of 
the ground. It has been mined throughout a length of about 300 feet. As a lode it is quite irregular, varying 
from a width of 20 feet to nothing, or expanding into large pockets of ore, and then contracting until the walls meet. 
It also throws off several branches, some of which return into the main vein. The shaft at present (1854) has a 
depth of about 150 feet, and an open drain meets the shaft about 20 feet below its mouth. 

This mine produces at present between seven and eight tons of excellent chrome ore daily, the fruits of the labour 
of three hammers and the attendant aid. The present price of the chrome ore is aboiit $25 per ton. The gross 
yield of this mine is therefore nearly $200 per day. The finer pieces of the ore are packed in barrels on the spot as 
they come out of the mine, and are thus sent to Europe without re-handling. The rest of the ore, after dressing and 
washing, is transported to Baltimore and other home markets. 

The Line Mim. — The other chief mine situated immediately on the boundary line of Pennsylvania and Maryland, 
and called therefrom " The State Line Mine," is not now actively wrought. Its shaft is about as deep as that of 
Wood's Mine. The aggregate former yield of the Line Mine amounted to several thousand tons. 

There are several interesting minerals associated with the chromiferous iron-ores and serpentine of this range of 
magnesian barrens, and nearly all the species occur equally at the two mines here spoken of. These minerals are 
enumerated in the general chapter on the mineral localities of the Primal district of the Atlantic Slope of Penn- 
sylvania. 

There is another shorter tract of serpentine barrens containing both the stratified and the unstratified intrusive 
varieties of the rock, situated about two miles north of the State Line in Lancaster County on the waters of the Cone- 
wango. The southern edge of this is near the little village of New Texas. The whole belt is about three miles long, 
and more than half a mile wide, and it has somewhat the form of a crescent, its convex curve being to the N.W. Its 
north-east end is about one and a half miles E. of the Conewango Creek, which it crosses aboTit two miles N. of 
the State Line, extending westward of the stream about a mile until its south-west extremity is within two miles of 
the Susquehanna, and a mile and a half N. of the State boundary. From this locality much silicate of mag- 
nesia has been taken, and transported to the chemical works of Baltimore and elsewhere, for the manufacture of Epsom 
salts and other preparations of magnesia. The excavation of this mineral is no longer pursued ; it was dug only in 
superficial pits. 

Titaniferous Iron Ores. — There are in the main serpentine belt of Lancaster four or five localities of titaniferous 
iron-ore, commencing near the Horse-shoe Bend of the Octorara, and ending about three miles E. of the Susque- 
hanna River. At one of these, on the farm of Mr Jenkins, some of this ore has been mined, but only to a trivial 
extent. A small amount of the same refractory variety of iron ore has been also dug on the shorter tract of serpen- 
tine barrens N". of New Texas. A more productive locality occurs near the Baptist Meeting-house, where several 
hundred tons of the variety called Bird-eye Iron Ore have been successfully mined. 

A careful examination of these two belts of serpentine near the State Line of Lancaster County cannot fail to 
convince any observant geologist that the material, ordinarily termed serpentine, as presented in these barrens, com- 
prehends both a stratified and an unstratified rock. Pure serpentine is here found only in the form of dykes 
intruded through a stratified serpentinous talcose rock, evidently a metamorphic clay-slate— the mica and talc-slate 
formation of the Susquehanna. The stratified serpentinous rock seems to have been impregnated with the magnesian 



172 



BELTS OF SERPENTINE. 



minerals during the intrusion of these veins of igneous serpentine. The evidences in support of this view are 
abundant in the ravines which intersect the barrens north of the village of New Texas. The genuine serpentine 
rock is itself a material of quite diversified aspect, some of it being of a dark-green colour, and very tough ; other 
varieties less dense and heavy, and much more easily fractured, and of a pale or yellowish green. This latter kind 
iisually abounds in contact with the chromiferous iron-ore at Wood's Mine and the other chrome localities. Certain 
small patches of the rock wear a slightly pinkish colour, but the predominant hue is some variety of green. 

The strata crossed successively in proceeding northward from the southern side of the more southern or main zone 
of serpentine near the Susquehanna, is as follows : — 

1. Hornblende gneiss and trap-rocks. 

2. Serpentinous talcose slates, with dykes of serpentine. 

3. Gneissoid, micaceous, and talcose slates, yielding a ferruginous soil, containing bands of whetstone or mica- 

slate. 

4. Serpentinous stratified talcose sedimentary rocks, full of intrusive, serpentine. 

5. An alternation of talcose, micaceous, and argillaceous slates, embracing the roofing-slate of the Peach Bottom 

Range. 

This latter group belongs to the older Primal slates, which extend all the distance to the Limestone Valley imder 
various remarkable conditions of metamorphism, some of them even simulating the ancient Gneissic rocks. 

At the State Line, five miles W, of the Susquehanna River, we find a small ridge of serpentine. It is about a 
mile long, and lies principally in Maryland. In this belt the mineralogist may obtain fine specimens of green 
serpentine, actinolite, chlorite, and asbestos, tintaniferous iron-ore and magnetic iron-ore. A band of chlorite slate, 
near the northern base of the ridge, contains, in abundance, beautiful octahedral crystals of the last-named mineral. 
About one mile northward is another smaller ridge of serpentine, like the serpentine belts of Chester and Lancaster 
counties ; that above described occurs in a lenticular form in the talcose and chlorite slates. 



Fig. 20.— Cleavage, N. foot of Bethel Hill, looking N.E. 



The following cut is introduced in illustration of a remarkable feature connected with the 

cleavage of the Primal slates described in this 
Chapter. It exhibits an instance of the segrega- 
tion of talc and quartz, in thin lenticular laminae, 
in planes coincident with the planes of cleavage, 
and obliquely transverse to the bedding of the 
rock. It is interesting as proving crystallisation 
to be the result of the same metamorphic influence, 
only more energetically exerted, which has caused 
the cleavage. The locality whence the drawing 
was taken, is at the N. foot of Bethel Hill. The 
strata dip steeply N. from the anticlinal axis of the 
Hill ; the cleavage obeys the usual law, and dips steeply S., and approximately parallel to the 
axis plane of the flexure, on the flank of which it occurs. 




CHAPTER 11. 



THE PRIMAL SERIES BOUNDING THE MIDDLE GNEISSIC DISTRICT. 

AVe may now trace the Primal wliite sandstone and slate as we find them developed N. of the 
Chester County Limestone Basin, and S. of the edge of the red sandstone. In doing this we 
shall have occasion to follow, first, the conspicuous and continuous zone, bordering the Chester 
County Limestone Valley on the N., under the name of the North Valley Hill ; in the second 
place, the Mine Eidge and its spurs, all of which are formed of this rock ; and in the third 
place, the Welsh Mountain and its dependencies. 

PRIMAL SERIES, WHITE SANDSTONE AND SLATES IN THE NORTH VALLEY HILL. 

Commencing W. of the Schuylkill about one mile E. of V alley Forge, the Primal white sand- 
stone of the North Valley Hill, so called, emerges into view from beneath the overlapping margin 
of the Middle Secondary red sandstone at the Eastern point of the hill known as Mount Sorrow, 
or that upon which Washington and his forces were encamped, amid great sufferings and 
privations, in the memorable winter of 1777-8. Here the Primal rocks, consisting chiefly of the 
older semi-crystalline slates, cross the East Valley Creek in a broad contorted belt, not less than 
half a mile in width. As we trace the formation westward, it would seem to expand rapidly, 
and to embrace a much larger portion of the white sandstone, and a less relative amount of the 
underlying Primal slate group. This change seems to take place in that section of the ridge 
which is called Mount Joy, for when we reach the Western point of Tredyffrin Township, or the 
vicinity of Ayer's Store, the chief rock visible is the white sandstone ; indeed, this is the case in 
the vicinity of Diamond Rock, though the north flank of the ridge at this latter point includes also 
a considerable thickness of Older Primal talcose slate. Throughout this part of its length, the 
belt of the Primal rocks is disturbed in dip by two or three closely-folded undulations, and it is 
in consequence of these that the sandstone at the Diamond Rock is spread over the Southern 
slope and summit of the ridge in so broad an outcrop. The lesser contortions and fractures 
connected with these undulations are the evident causes of the numerous veins and cavities, filled 
with crystals of quartz, which occur in the compressed and fractured masses of the sandstone at 
Diamond Rock, and which have conferred upon this cliff its name. A partial interruption in 
the continuity of the North Valley Ridge occurs at the depression above Ayer's Store, and it would 
seem that the outcrop of the Primal rocks takes here a sudden offset northward, the result, 
apparently, of the cessation of the undulations prolonged thus far from the Eastern end of the 
ridge, and the introduction of one or more new anticlinal waves in the strata extending from 
this point westward. It is pretty obvious that near Ayer's Store, almost the whole of the broad 
outcrop of the Primal rocks has been swept from off the gneiss, and only a single monoclinal line 
of the sandstone left at the base of the hill in contact with the limestone of the valley. From 
this jog or local change in its course, the Primal belt ranges with remarkable straightness towards 



174. 



NORTH VALLEY HILL. 



tlie W.S.W., and with no actual interruption, until in Lancaster County it coalesces with the 
range bounding the Limestone Valley on the S. It presents, however, several decided fluctua- 
tions in its breadth, due to changes in the dip, and especially to the introduction of a less or 
greater number of narrow anticlinal undulations in it. The structure of this zone is pretty well 
exposed in all the principal gorges through which the tributaries of the Brandywdne and the 
Octorara drain through it in their progress southward. In these natural sections, though the 
edges of the strata are generally much obscured by fragmentary rubbish and soil, it is easy to 
detect the presence of usually two, and sometimes even, three, closely-folded anticlinal plications, 
the dip being generally at a high angle to the S.E. From the changes which arise in these 
flexures, the breadth of the whole belt varies from a quarter of a mile in some places to at least 
three-quarters in others. In sundry cases we may detect sharp saddles, or anticlinal uplifts of 
the subjacent gneiss rocks, subdividing the whole belt, at least at the level of the beds of these 
transverse valleys, into a succession of parallel, closely-folded, synclinal troughs. In some 
instances the lower strata of the Primal series, thus brought up on the back of the gneiss, is so 
crystalline and gneissoid from metamorphic action, especially where it is contiguous to dykes of 
intrusive granite, that to determine always the boundary which separates the two sets of rocks 
is by no means easy. 

For several miles E. of the East Branch of the Brandywine, there seems to be but an insignifi- 
cant thickness of Primal talcose slate associated with the white Primal sandstone ; but approaching 
the West Branch of that stream, or the vicinity of Coatesville, both the upper and lower Primal 
slates appear in the series in rapidly and steadily augmenting force. There is no feature 
connected with the Primal rocks of this district of Pennsylvania so remarkable as their appear- 
ance and disappearance within the narrow limits of a few miles. This fluctuation is perhaps most 
conspicuously exhibited in the striking contrast presented in the composition of the North and the 
South VaUey Hills between Valley Forge and Downingtown, in which district it has been already 
shown that there is on the South side of the limestone even a total absence of the white Primal 
sandstone, or a bed of it so thin as generally to escape detection ; while on the North side of the 
valley the formation is developed under a thickness of at least 50 feet at Diamond Rock and 
elsewhere. Again, to the S. of the basin there appears to be a vast expansion of the lower 
Primal slates in their metamorphosed condition of talco-micaceous slates ; but to the N. of this 
great trough, at a distance no greater than two or three miles, there is a great deficiency of this 
schistose group. (See Fig. 25, Section through Coatesville to mouth of Buck Eun, at the end of 
this Chapter.) It Avould seem that both the sandstone and the argillaceous or slaty members 
of the series had in this part of their original area been thrown down in irregidar patches, and 
in beds of quite inconstant thickness. When we reach the West Branch of the Brandywine, and 
examine the constitution of the Primal series there, or study it in sections still further W., we 
are struck with a marked difference of type compared wdth that which it possesses at or E. of 
Downingtown. Near the latter place, at the pass of the Brandywine, through the North VaUey 
Hill, the Primal slate is almost wanting ; and the white sandstone, folded in several successive 
waves, seems at first, until these are recognised, and their influence estimated in multiplpng the 
thickness of the belt, to be a formation of enormous depth, whereas it nowhere in reahty 
surpasses 100 feet. The first outcrop of the rock, or that which bounds the valley, presents the 
sandstone in its usual indurated or slightly vitreous condition, and in this characteristic state it 



DIAMOND KOCK. 



17.5 



contains in the thin partings separating its remarkably parallel layers, delicate coatings of pure 
white talc ; while imbedded in the surfaces of the sandstone are numerous very small needle- 
shaped crystals of black schorl, always more or less broken, as if from a difference in the law of 
shrinkage, or cooling of the rock and the mineral. The other outcrops or folds of the stratum 
which lie further N., and nearer to the border of the gneiss, and which are more injected with 
igneous granite, show a still more advanced stage of metamorphism. There the rock consists of 
an excess of granular quartz, involving specks of crystalline felspar, the presence of which, and of 
the included talc, renders it sometimes difficult to distinguish the altered stratum from some 
fine-grained white granites. The schorl is, however, a sure guide to the recognition of the sand- 
stone, however altered. 

Fig. 21.— Section, Diamond Rock to Paoli, looking N.B. 




. State* tutco-micat. 



An inspection of the Sections across the Chester County Valley and its north and south bounding 
hills, one extending from Phoenixville to the Paoli, another along the East Branch of Brandywine 
through Downingtown, and the third through Coatesville by the West Branch, will serve to show 
the relative development of the different members of the Primal series in these different districts, 
and by comparison, exhibit those remarkable fluctuations in their dimensions to which we have 
alluded. This comparison will show that, while in the two Eastern sections very little Primal 
talc-slate occurs on the North side of the valley, the series embraces at Coatesville an enormous 
preponderance of the slates over the white sandstone, the upper Primal slate having a thickness 
of at least 700 feet, while the chief bed of the white sandstone measures no more than 30 or 35 
feet, (See Sections.) 

Fig. 22.— Section North of Coatesville, looking N.E. 




Following the formation westward along the same outcrop N. of the valley, we find it well 
exposed near Parkesburg, at the passage of Buck Eun through the ridge. Here the belt appears 
to contain three outcrops, in a denuded, anticlinal, and synclinal flexure, its whole width from 



Fig. 23.— Section, HiU North of Parkesburg, lookhig N.E. 







J 1. . 


i:: v,:l ft ^ 


:. i . ,:;.,\.V^M||:TO^ 












330 :;o 340 




0" 

r- 






i 

i' Pr. SJtl. 


Pr. N. Slale, 





the limestone to the gneiss being a little less than one-third of a mile. In the vicinity of 
Parkesbiu'g the strata, in descending order, are as follows : — 



176 



PRIMAL ROCKS, MINE RIDGE. 



1. The upper or newer Primal slates, possessing a total thickness of about 700 feet, are subdivided by an inter- 
calated thin bed of yellow sandstone, situated here very near the middle of the group, which may be regarded as the 
upper Primal sandstone of Coatesville and Chiques Ridge. Above this upper sandstone there are 300 feet of thinly- 
laminated micaceous slaty strata — internally, olive brown — externally, very brown and ferruginous. These contain in 
their lower part thin layers of white sandstone. 

The yellow sandstone is itself about 200 feet thick, and between it and the micaceous slate occurs an alternation 
of thin and slaty layers of sandstone with the ordinary Primal slate. Underneath the yellow sandstone there succeeds 
another group of laminated slaty strata, some 350 feet in thickness, resting upon the upper beds of the main deposit 
of white Primal sandstone. 

2. The middle or white Primal sandstone member of the series is in this neighbourhood about 50 feet thick. 
In its southern or first outcrop, north of Parkesburg, it is quarried in one or two places, and being veiy evenly and 
thinly bedded, it affords large slabs, well adapted for building and for flagging. On the surface of some of these we 
discern the characteristic broken crystals of black schorl in more than usual size and abundance. 

3. The lower member of the Primal series, a thick group of brown silicious slates, more or less talcose and 
micaceous, is generally too much obscured at its outcrop by a covering of fragmentary matter, derived from the sand- 
stone crest of the ridge, and from the adjoining gneiss, to enable us accurately to estimate its thickness ; but this 
cannot be less than 300 or 400 feet. 

These strata, especially the upper and the middle groups, are well exposed on the Strasburg Turnpike, immediately 
north-west of Parkesburg ; and the middle member, or the white sandstone, conspicuously so in the gorge of Buck 
Run, one mile east of the village. 

Under about the same type, the Primal rocks range forward to the AVestward into Lancaster 
County, and we meet them in approximately the same relative development in their next out- 
crops to the N., namely, in the Mine Eidge at its Eastern spurs. 

This narrow regular belt of the Primal strata in the North VaUey Eidge keeps its course 
insulated between the Auroral limestone on its S., and the gneiss on its N., the whole way 
to the Westernmost Branch of the Octorara Creek in Bart Township, where, by the cessation 
of the gneiss, it coalesces with another and broader belt of Primal rocks, that of the Mine Eidge. 
To the description of this belt we next proceed. 

Fossils. — The only fossil known to exist in the Primal rocks in Pennsylvania, the Scolithm linearis, is to be met 
with abundantly in the Primal white sandstone in the line of outcrop we have been tracing, especially in that portion 
of it which is embraced between Downiugtown and Valley Forge. At the foot of the ridge, for a mile east of Ayer's 
store, specimens of this simple cylindrical form, arranged perpendicularly to the bedding of the sandstone, are 
numerous by the roadside. 

MIDDLE BELT OF PRIMAL ROCKS NORTH OF THE LIMESTONE VALLEY, OR THAT OF 

MINE RIDGE AND ITS SPURS. 

Between the synclinal trough of Auroral limestone terminating westward in Drumore, or 
the same basin prolonged through the Primal rocks to the Susquehanna, near M^Call's Ferry as 
a Southern limit, and the South edge of the limestone of the Pecquea and Conestoga Valley, there 
spreads a broad undulated tract of the Primal rocks, embracing a number of short, narrow, 
insulated basins of Auroral limestone, divided from each other by anticlinal waves, which 
elevate the lower Primal slates to the surface, but nowhere bring to view the subjacent gneiss 
rocks. 

In this district the more prominent stony ridges consist of the Primal white sandstone, but 
by far the largest extent of the surface eastward of Big Beaver Creek, a tributary of the Pecquea, 
belongs to the Primal slates. There we may recognise a series of little limestone basins. This 



MINE RIDGE. 



177 



general anticlinal zone rapidly contracts as it extends Eastward between the range of gneiss, which 
now bounds it on the S, and the limestone of the Pecquea basin on its N. It there begins 
to take the name of the Mine Eidge, and under this title extends until it is opposite the Eastern 
end of the Pecquea Basin. The narrowest and lowest part of this ridge is at the notch called the 
" Gap," through which the Columbia Eailroad passes, and where its summit is not quite 500 
feet above the level of the ocean. The width of the ridge, or rather of the belt of Primal rocks, 
in this vicinity, does not much exceed half a mile. There, and to the Westward for some 
distance, the structure of the Mine Eidge is very simple ; it is composed of the three members 
of the Primal series already described, the white sandstone being in considerable relative force, 
and the whole undulated into one synclinal with one anticlinal wave ; or, in other words, 
into three moderately gentle dips. That margin which reposes against the gneiss, dips rather 
steeply from it, or Northward ; but this dip is succeeded near the gap, or central crest of the 
ridge, by an anticlinal flexure making a South dip and a second North one, the beds affected b ythe 
latter descending beneath the limestone at the foot of the hill. Advancing "Westward, the only 
difference in the structure of this elevated zone of the Primal rocks is, that additional anticlinal 
flexures introduce themselves from the Westward into the belt, until in the longitude of Big 
Beaver Creek we may count at least six of these waves. 

In the opposite direction, or Eastward from the " Gap," the structure of the Mine Eidge 
becomes complicated in a different manner by the appearance of a succession of anticlinal spurs 
N. of the main crest. If we trace this out to its Eastern termination, we shall find it ending 
W. of the West Branch of Brandywine in a long trough or synclinal point, and N. of this we 
may notice a long narrow anticlinal belt of the Gneiss rocks coming in from the E. to divide this 
spur of the Mine Eidge from another basin of Primal strata lying yet further N. in the centre 
of West Cain Township. Nearly W. of this uplift of the Gneiss rises an anticlinal spur of the 
Primal sandstone, N. of tlie true Mine Eidge, and projecting forward into the South-eastern 
corner of the limestone basin of the Pecquea, enclosing a little synclinal cove of that limestone 
between it and the main ridge. StiU advancing Northward to the North boundary of Cain and 
West Brandywine townships, we reach another and much longer synclinal belt, prolonged from 
the Mine Eidge, but quite out of line with it. This is divided in part, or towards the E., by 
a narrow strip of uplifted and denuded Gneiss, penetrating across the West Branch of Brandy- 
wine, some three miles, to within a couple of miles of the limestone in the neighbourhood of 
Compassville. It is probable that the anticlinal wave which uplifts this second belt of Gneiss is 
the same with that which arches into a ridge or spur of the Primal rocks a little N. of the 
above-named village. In any case, it is obvious, from the structure and topography of the 
district, that the two or three successive spurs which protrude themselves Westward into the 
Limestone VaUey, to enclose as many lesser valleys or synclinal coves of the Auroral strata, are 
the results of the gradual declension in that direction of so many undulations that further East- 
ward are in sufiicient force or elevation to hft out the Gneiss. 

The most Northern of the three syncHnal ranges, into which that of the Mine Hill may be 
said to expand itself in its progress Eastward, terminates in a low point W. of the North Branch 
of the Brandywine, near Springtown Methodist Church. Traced thence Westward by the JManor 
Presbyterian Church, it extends in a widening belt, and, crossing the West Branch of the Brandy- 
wine, becomes the broad and but little cultivated belt known as the Barren Eidge, the crest line 
VOL. I. z 



178 



PRIMAL ROCKS NORTH OF CHESTER VALLEY. 



of which follows nearly the boundary between West Cain and Honeybrook townships. The 
Northern edge of this belt is defined by the Southern margin of the Gneiss from Indian Run 
Valley to the Pecquea. 

Between the Western end of this belt, which may be viewed as terminating near the line which 
separates Chester and Lancaster counties, and the South-western end of Welsh Mountain, there 
extends, nearly in its line of prolongation, a narrower outcrop of the Primal rocks intervening 
between the Gneiss on the W. and N., and the limestone of the Pecquea basin. It is 
probable, however, that this strip of the sandstone along the margin of the valley is not every- 
where discernible, for the district presents indications of a succession of faults, extending West- 
ward from the Gneiss into the limestone, and bringing these two formations into contact by 
engulfing and hiding from view the interposed Primal series. 

NORTHERN BELT OF PRIMAL ROCKS NORTH OF THE CHESTER COUNTY VALLEY, 

WELSH MOUNTAIN, &c. 

The third and last principal belt of the Primal strata N. of the Limestone Basin of Chester 
County, is that of the AVelsh Mountain and its Spurs. It commences about four miles E. of 
Morgantown, where the Mesozoic red sandstone overlaps the end of the ridge, and extends in a 
direction a little S. of W. to a point about two miles south of the \dllage of New Holland. 

In this belt the white sandstone is not as firmly cemented a rock as it is in the North Valley 
Hill. Advancing Westward, the ridge assumes a more systematic anticlinal form (see general 
Section V.), the sandstone dipping in both directions beneath the Matinal limestone ; and as the 
axis sinks, the upper slates, which are of a dark-brown colour, occupy the surface, and hide the 
sandstone. Where the axis is high, as near the Sorrel Horse Inn, two and a half miles from 
Churchtown, the sandstone formation exhibits marks of much more igneous action than in other 
parts of the range. It is partially vitrified, very compact, and traversed by innumerable planes 
of cleavage, with imperfect crystallisation. This is not the result of contact with any ig-neous 
rocks, for the nearest trap-dyke is distant more than half a mile, and has produced but little 
alteration in the limestone in its immediate neighbourhood. 

In this belt we meet with all the three divisions of the Primal series which characterise it in 
the North Valley Hill, and in Chiques Ridge at the Susquehanna ; but the Primal white sand- 
stone member appears to be in yet greater force than in any of the outcrops situated to the 
S.E. The general structure of the main Welsh Mountain seems to be very analogous to 
that of the Mine Ridge near the " Gap." In other words, it consists of an anticlinal and a 
synchnal wave, and, towards its Western end, appears to be still further complicated by the 
rising of another shorter anticlinal, entering it from the Gneissic district to the E., to form its 
Westward spur. The upper or newer Primal slates, reposing upon the white sandstone, are in 
some places excessively ferruginous at their uppermost limit, where they alternate with the lower 
beds of the Auroral magnesian limestone, so that large accumulations of iron ore may be looked 
for at the North base of this ridge, where the limestone of the Morgantown or Conestoga Valley 
is in contact with its strata. It is precisely under these relations, both as respects the geology 
and the topography, that the large mine called Jones's occurs near the head of that limestone 
valley, two and a half miles N.E. of Morgantown. 

I have intimated in another chapter, that there exists a prolongation of this band of Primal 



BLACK HORSE HILL. 



179 



rocks, not quite in line with the axis of the Welsh Mountain, but nearly a mile to the N, of 
it. This belt extends from near Jones's Mine eastward for about three and a half miles to 
Pine Creek, terminating about one and a half miles N. of the Warwick Iron Mines. Like 
the Welsh Mountain, it has a stony surface, a sandy and sterile soil, and is covered almost 
entirely with forest. These two Primal ranges are probably connected by a neck of the same 
strata between Springfield and Jones's Mines ; but the surface there being low and much obscured 
by the untilled swampy tracts which form the water-shed between the Conestoga and the South 
Branch of French Creek, the continuity of the Primal strata cannot be easily made out. 

The extreme Western point of the Primal strata of the Welsh Mountain is at Mill Creek, near 
the Old Peters Eoad. The Welsh Mountain is the N.W. boundary of the Gneissic district of 
Chester County. From its Western spur, the view over the fertile and highly-cultivated plains 
of the Conestoga is, in the month of June, when the crops are ripening, extremely attractive, for 
this is one of the most fertile and best-tilled of all the grain-fields of the United States. The 
charm of the landscape, in which the middle distances abound in all the features of agricultural 
beauty, is not a little enhanced by the contrast between the fertility of the plain and the wilder- 
ness-like aspect of the background of forest-covered hills, or mountain-spurs, by which the scene 
both S. and N. is bounded. 

INSULATED ANTICLINAL RIDGES OF PRIMAL SANDSTONE. 

There is a low insulated hill of the Primal rocks a little N. of the Welsh Mountain, and rather 
more than one mile W. of Churchtown. It is somewhat more than one mile in length. Its 
structure is anticlinal, and the limestone on both sides dip from it. It marks the position, 
therefore, of a flexure of some magnitude. 

Another rather longer tract of very similar form is situated about three miles N. of 
Lancaster, near NefisviUe. This is likewise anticlinal in its structure, is surrounded by the lime- 
stone, and is the crown of a short axis, of which there are many in the adjacent limestone 
which do not thus protrude the Primal series. 

INSULATED BASIN OF SEDIMENTARY STRATA WITHIN THE NORTHERN GNEISSIC 

AREA OF CHESTER COUNTY. 

That there should occur in the interior of the Gneissic district of Northern Chester County 
one or more insulated synclinal belts or troughs of the Palaeozoic strata, ought not to surprise us 
after what has been already disclosed of the existence of a succession of anticlinal and syuchnal 
undulations in the Western part of the district, and of the series of synclinal dislocated basins in 
the very heart of the region, containing long lines of iron ore. The most conspicuous detached 
basin of newer rocks, resting within the Gneiss, is one in the West corner of West Vincent Town- 
ship. It is a long belt of Primal white sandstone, which here forms a regular ridge elevated 
above the general rolling plain of the Gneiss rocks, and known in the neighbourhood as the 
Black Horse Hill. Its length is about two miles, and its breadth is not less than 2000 feet. 
From the crumbled condition of the sandstone at its outcrops, and the absence of any quarries 
or good natural exposures, it is impossible to recognise the dip of the strata ; but that these con- 
stitute a synclinal belt or outlying trough is very obvious. It is worthy of note that this tract 



180 



PEDIAL EOCKS, NORTH VALLEY HILL. 



of Primal sandstone lies nearly in the range of the long sjuclinal trough of that rock, forming 
the hilly belt kno^A^l as the Barren Eidge west of the North and West Branches of the 
Brandy wine. 

COMPOSITION AND LIMITS OF THE PEIMAL SEEIES OF THE NORTH VALLEY HILL 
NEAE VALLEY FOEGE AND V'ESTWAED. 

That section of the North Valley Hill which extends from its Eastern termination E. of 
Valley Forge to Lancaster County, contains all the three upper formations of the Primal series 
in fuU development, though* from metamorphic action, under a greatly-altered aspect. The 
main central crest of the ridge marks for the most part the outcrop of the sandstone or middle 
member of the series, while the lower Primal slate occupies the Northern flank, and the upper 
Primal slate the Southern. 

These slates have each a thickness of several hundred feet, but the sandstone embraced 
between is nowhere of great bulk, indeed seldom exhil^iting a diameter of a few yards, and 
nowhere 100 feet. The slates are chiefly silico-argillaceous rocks, as may be easily seen, where 
they are in their normal condition in the belts further to the N.W. There they are ordinar)' 
sandy slates, with included beds of argillaceous sandstone ; but along these more metamorphic 
Southern ranges bordering the Chester County Valley, their structure and aspect display almost 
the extremest degrees of metamorphism of which argillaceous strata are susceptible. 

The visible boundary of the Auroral limestone, as marked by the overlajijping edge of the 
Mesozoic red sandstone, is traceable from Port Kennedy to near the Eastern point of the North 
Valley Eidge ; but at the foot of Mount Sorrow the slates of the Primal series emerge to view in 
contact with the margin of the red sandstone, and from this point forward to the W., as far as 
the point of first appearance of the Gneiss, the border of the Primal slate is defined by the undu- 
lating boundary of the red rocks — namely, over the Northern flank of Mount Sorrow, and across 
Valley Forge Creek at the Dam. But from the Eastern apex of the belt of gneiss near the Baptist 
Church, the margin of altered Primal rocks defined from this point onward by that formation, 
trends off" somewhat more South-westward, assuming a higher position on the Northern slope of 
the main ridge. The precise place of the line of contact of the Primal and Gneissic rocks is not 
susceptible, in many parts of the ridge, of exact determination ; yet the boundary can be 
sufficiently well inferred from the external features, the change in the soil, and the sm'face frag- 
ments. Guided by these signs, and by occasional outcrops of both formations, we can follow the 
limit along the Northern slope the whole way to the point in the spur of the ridge where this 
first breaks down at the passage of the road which leads down its flanks into the valley, and also 
at Ayer's Store. From the Valley Forge Creek to this gap or depression, the ridge is very 
straight, even, and continuous, and is everywhere crowned by the outcrop of the hard, altered 
Primal sandstone, which appears to have been trenched away by a rush of waters through this 
depression. Here, and at the crossing of the road from Pickering Creek towards the Paoh, it is easy 
to recognise, on the Southern slope of the ridge, the ujjper Primal slate in the condition of a talco- 
chloritic ciystalline slate ; but it is more diflicult to detect the lower Primal slate of the Northern 
slope of the hill. This is beautifully exposed at Valley Forge Creek, is cut in the Pennsylvania 
Mining Company's shaft, and is visible frequently in fragments on the Paoli and the other roads 
over the ridge ; but it is not generally discernible in place, being extensively covered by the 



IRON ORES. 



181 



fragments and the sand of the Primal sandstone of the crest of the ridge, swept over it by 
retreatino; waters. 

The actual constitution of these Primal schists is that of talco-chloritic slates, in which the 
talco-chloritic and quartz constituents are distinctly segregated, and in many portions thoroughly 
crystallised. Indeed, so completely are these masses converted to the structure and composition 
of the talco-chloritic schists of the genuine Gneissic family of rocks, that they have hitherto 
been invariably referred to that group ; and it is with much difficulty that a geological observer, 
not intimately acquainted with the phenomena of metamorphism in the rocks of our Atlantic 
Slope, can persuade himself that these are genuine Palseozoic masses, or beds of a fossiliferous 
age, converted by mere igneous agency to the antique aspect they present. But a study of the 
gradations or alterations assumed by these strata, as they may be traced from the zone of 
maximum change to the districts of least transformation further N.W., puts the correctness of 
this conclusion beyond all doubt. 

The Primal sandstone, as it presents itself along the two lines of outcrop bordering the Chester 
County Valley, exhibits nearly all the varieties which belong to it where it is thickest and most 
largely developed elsewhere, whether we compare it with the Potsdam Sandstone of New York, 
or with the mountain masses flanking the North-western slopes of the Blue Eidge in Virginia 
and the States further S. Here in Chester County it contains, besides its typical beds of pure 
white and yellowish white quartzose sandstone, some other members, especially coarse loosely- 
aggregated sandstones, and fine-grained silicious conglomerates. Notwithstanding the excessive 
heat to which these rocks have been subjected, they have not been at all fused, nor have their 
obscure organic relics been obliterated. Indeed, the Primal sandstone of the summit of the 
North VaUey Hill contains in great abundance, even where it has been baked and indurated, the 
curious stem-like fossil, the Scolithus linearis, so distinctive of this formation. Thouo;h con- 
vinced for many years past, from structural evidence, that this crest rock is the true Primal or 
Potsdam sandstone, yet my recent discovery (in July 1853) of this organic form, the earliest 
type of living organism in any American formation, affords a satisfactory confirmation of the 
soundness of the deduction. 



Fig. 23 a. — Section from North Valley Hill through Coatesvillc, to mouth of Buck Run on Brandywine. — 1 inch = 2^00 feet. 

- ■.J.,>.-^--"r\ ..'.S-. », «■ -i. -o " >■-. jX>-.'.\\a a<..:»A^^.v 

Talc. !r Talc. Miai. Slain 

lEON OEES OF THE PEIMAL STEATA. 

Jones's Iron Mine in the Southern Cornei' of Berks Count;/. — This extensive 
and valuable iron-mine belongs to the Warwick Iron Company. It is near the 
Mic. jirg,i. SI. Fiae.vkasia,, 0'^'^ eastsm Bxtremitj of that branch of the Conestoga Limestone Basin of Lancaster 

County, which extends into the southern angle of Berks, under the name of the 
Morgantown Valley, N. of the Welsh Mountain. The mine is about two and a half miles north-east of Morgan- 
town. Its geological position is in the upper Primal slates, just at the base of the Auroral magnesian limestone. 
More correctly, this ore is the upper Primal slate itself, or its highest beds rather, in a very ferruginous condition. In 
this and several other respects its relations are strictly the same as those of the great iron-ore deposit of the Cornwall 
Mines in Lebanon County. 




182 



lEON ORES OF THE PEBIAL STRATA. 



Tlie chief mine is an open excavation, covering rather more than five acres ; and there is another to the south of 
it occupying about one acre. Magnesian limestone boimds the ore on the northern edge of the principal excavation. 
Here there is a mine-shaft 1 80 feet deep, with a competent steam-engine. The shaft enters the limestone at a depth 
of 50 feet from the surface, and a boring, descending 20 feet from the bottom of the shaft, is still in this rock. 

A dyke of trap-rock cuts the ore-bearing strata near the southern side of the pit, and produces phenomena pre- 
cisely identical with those caused by the trap-dykes in the Cornwall Lebanon Mines, converting the ore to a more highly 
crystalline form, and endowing it partially with magnetism. As in every such instance, the ore is richest and purest 
adjacent to the trap-dyke. This is equally the case in the southern or smaller mine. The strata dip to N. 30° W. 
at about 20° ; and in the northern bank of the large mine, we may perceive the Auroral hmestone regularly overlying 
the upper beds of the Primal slate, containing or consisting of the ore. 

This mine has been wrought with more or less activity for the past seventy yeare. Its product in 1853 was about 
7000 tons, and this is stated to represent the average yield for the last twenty yeai-s, while for the previous fifty years 
the annual amount furnished is given at about half as much. 

In this mine, as in that of Cornwall in Lebanon, some of the ore contains a small amount of copper, in the form 
chiefly of sulphm-et, carbonate, and silicate of copper. To extract this copper ore has been a favom'ite thought with 
some metallurgists for several years past, and about five years ago, an elaborate and expensive experiment was under- 
taken with this object by the American Mining Company of New York. They erected at the mines machinery for 
crashing and grinding the ore, and a costly apparatas, consisting of cylinders bearing a multitude of magnets and 
brushes for withdrawing the pulverised magnetic oxide of iron fi-om the copper ore, and other constituents. This 
enterprise has proved to be unprofitable, partly from the difficulty of eflecting a thorough separation, partly from the 
want of a sufficient abmidance of the essential element, the copper ore. Including the cupreous iron-ore mined within 
the four years of this undertaking, the whole annual product was not less than 10,000 tons. 

Iron Ore Bank of Chestnut Hill, near Columbia. — This large mine is situated about three and a half miles north- 



Pt. Sandtt. floor 



Fig. 24.— Chestnut Hill Ore Bank, 3 miles N.E. of Columbia, Lancaster County. — 1 inch = 500 feet. 

east of Columbia, in a high trough-like valley or basin on the slope of Chestnut Hill, a spm- of Chiques Ridge. The 
structure of the valley is apparently synclmal, the dips gentle, and in the central portions nearly flat. The ore lies 
in the lowest layers of the Primal newer slates, the very same formation which contains the ore in the Cornwall, 
Jones's, and Safe-Harbour mines. As the mine is now developed, it is perhaps the clearest illustration the region 
afibrds of the geological relations of the Primal ore. It is worked by benching or open quarrying, the whole material 
enclosing the ore being in many parts cut down perpendicularly in steep banks. The depth in the centre of the big 
mine, from the soil to the bottom rock supporting the ore, is about 100 feet, and ore of greater or less richness 
prevails throughout this entire thickness. 

The present excavation (1856) covers nearly the whole of the tract of ground belonging to this one estate — namely, 
about eleven acres ; but xmdoubtedly this is not the full extent of the ore-bearing ground. Indeed, the existence of a 
rich large mine, owned by the Messrs Grubb, almost half a mile to the eastward, shows that the ferruginous deposit 
has a wide range. 

The ore-embracing stratum has been dug through to the supporting rock in several places. In each such instance 
the floor is the upper surface of the Primal white sandstone. In some places the first layers of this rock are a pale 
yellowish sandy slate ; but, penetrating a little farther, the hard white sandstone invariably appears. It would seem, 
therefore, that the ore aU lies within the first 80 or 100 feet of the newer or upper Primal slate. This slate, throughout 
the upper 40 or 60 feet or more— the thickness varying with the amount of the formation — is now in a thoroughly 
disintegrated condition, being in the condition for the most part of a bluish, yellowish, and white laminated unctuous 
clay ; but it stiU retains, more or less distinctly, the stratification or intimate foliation of the original slate. Though 



■ - .w; 



CHESTNUT HILL. 



183 



approximately horizontal, the layers display a wavy bedding, the result seemingly of an undulation of the strata 
primarily impressed, and not a consequence of any washing in of ore or clay deposits. 

Beneath this rather regularly bedded ore-containing slate, there lies throughout a large part of the mine an irregu- 
lar deposit or bed of rich solid concretionary ore, extending under a variable thickness of 10, 20, and 30 feet, down to 
the top of the Primal sandstone. (See Fig. 24 a.) 

It is evident that this ore, which is a brown cellular fibrous haematite or limonite, has been derived from the filtra- 
tion of the oxide of iron, from out the fen'uginous slates above, which show in their condition of meagre clays, that 
they have been thus completely leached by water. The surface of the Primal sandstone is even now a water-bearing 
plain, for it is only here that water is met in sufficient quantities for domestic use, in and near the mine. Consoli- 
dated layers of the brown ore are also seen overlying certain of the more impervious layers of the clay-slate, as if this 
also at one time arrested the descent of the ferruginous particles. 

Possibly a part of the undulation of the strata may be due to the upward bulging action of the ore, as this was 
accumulating and concreting from above, such as we know took place in the gypseous strata of Western New York 
from the collection of great cakes of plaster on an impervious floor of shale. 

An interesting inquiry is here suggested as to what can have been the geological atmospheric condition which pro- 
duced the remarkable percolation which carried down so large an amount of ore out of these ferruginous beds. Was it 
tepid rain, charged with carbonic acid, in an early Palaeozoic period 1 or could it have been a long filtration of surface 
waters, such as now soak the earth ? or are we to surmise an action of internal steam issuing upward through crevices 
in the strata, in a period of crust-movement and disturbance? I am inclined to the first conjecture. 

It is worthy of note, that only in one spot in the mine do we meet with a crystalline magnetic ore. In the old or 
large mine there is a band of this ore, three or four inches thick, containing small but beautiful octahedral crystals ; 
evei-ywhere else the ore is the common brown peroxide of iron. From this fact it would appear that this Chestnut 
Hill deposit was invaded by a less energetic metamorphic action than that which attacked the Cornwall and Jones- 
town strata, where the crystalline and magnetic condition, due to heat, is the prevailing state, and not the exception. 
At what stage or period did this metamorphism of the ore take place ? Was the oxide of iron of the Cornwall and the 
Jones's Mine primarily deposited as a part of the slate, and crystallised at the time of the metamorphism of all the 
Paleeozoic rocks 1 or did the ore originate from out of the ferruginous slate by a process of percolation, bringing 
together its particles, previously intimately diffused there, the heating, altering action arising afterwards ? I am dis- 
posed to think that the ore was collected from the substance of the rock, and then metamorphosed. But this is at the 
present a somewhat obscure inquiry. Probably the Palteozoic masses underwent more than one action of upheaval, 
undulation, denudation, and metamorphism ; one perhaps at the end of the Matinal age, and a final one at the close of 
the Coal period. 




Pig. 24 a.— Section of Iron Ore at the base of the Primal Slate, Chestnut Hill Mine. 



CHAPTER III. 



PRIMAL STEATA ON THE SUSQUEHANNA AND IN YOEK COUNTY. 

The Primal rocks occupying the Southern townships of Lancaster County, and the whole 
South-eastern angle of York County, are admirably exposed for geological study in the deep and 
cliff-lined valley of the Susquehanna, from Marietta to the Tidewater at Havre-de-Grace. I pro- 
pose, therefore, to illustrate this portion of the Southern zone by a detailed description of these 
strata, as they are displayed along the West bank of the river, where the fine natural section 
has been aided by numerous cuttings for the Tidewater Canal, appealing to the elaborately con- 
structed profile of the rocks for future elucidation of the structure and features of the region. 
One such carefully-compiled continuous section furnishes a better conception of the geological 
composition of the district, than any multitude of unconnected notes drawn from detached 
localities. This has been surveyed and drawn up with care, and will therefore supersede the 
necessity of much detailed description of the surface phenomena of the Slate country E. and 
W. of the river, where, in truth, there is extremely httle variety in either its geology or 
mineralogy. 

DESCEIPTION OF THE SUSQUEHANNA SECTION. 

The Susquehanna River, throughout its entire length from Marietta to where its waters merge into those 
of the Chesapeake Bay at Havre-de-Grace, occupies a deep broad vaUey,varying in width from a few hundred feet 
to more than a mile. On either shore it is for the most part bounded by rocky bluffs supporting table-lands, 
at an elevation of from 1 00 to 500 feet above its waters. These bluffs exliibit a grand natural section of the 
whole group of the I'rimal series, constituting the base of our Palteozoic system. 

Leaving the Auroral Limestone Valley of York and Wrightsville at Creitz Creek and proceeding South- 
ward, we pass a belt of hills about two miles in width, which elevate Primal rocks high above the river-level. 
They indicate the presence of at least two folded anticlinals, which, coming in from the South-west corner of 
York County, cross the Susquehanna below Columbia, and droop away at the West Branch of the Little Cone- 
stoga Creek, where the limestone laps around the base of the hills. In a little cove between these two anticlinals 
exists a narrow trough of impure limestone, seen on both banks of the river. In the hill N. of this cove, 
there is no appearance of Primal sandstone, the strata consisting exclusively of the Primal upper slates. Under 
conditions of partial metamorphism, they present themselves as dark-blue silicious slates, with the cleavage smfaces 
glazed, and in some places speckled with crystals of sulphuret of iron. The wider belt of Primal strata below 
the cove, like the former, is chiefly slate. There are two bands of Primal white sandstone, neither of which 
exceeds one hundred feet in thickness. If our construction of dips is correct, they form the two limbs of the 
folded anticlinal. 

It should be observed that the planes of true bedding are very obscure, being almost entirely obliterated by 
the cleavage, which intersects the rocks by an infinite number of parallel planes. The planes of cleavage are 
nearly or quite parallel in strike with the planes of bedding, though they dip at a high angle, ranging from 70" 
to 90° S., 15°- 20° E. 

This wide anticlinal belt of slate stretches southward m an almost straight com-se, with a slight increase in its 
breadth, entirely across York County, into the extreme South-east corner of Adams County, and thence into Mary- 



PRIMAL ROCKS, SUSQUEHANNA RIVER. 



185 



land. It is bounded N.W., throughout its whole length, by the York and Hanover Limestone Valley, or that 
of the main Codorus and Creitz Creeks, and S.E. by the narrow limestone trough of Cabin Branch Run, and the 
other shorter limestone basin of Jefferson. The structure of this belt is that of a broad flattened anticlinal 
arch, with one or even more synclinal depressions in its middle. Only in a few localities does it expose Primal 
white sandstone. 

A somewhat promising locality of roofing-slate occurs in this ridge about two miles south of the York and 
Wzightsville Railroad. 

One mile south of Hanover, we meet the line of contact between the limestone and slate ranging N.E. 
and S.W,, and, passing half a mile south of Littletown, bringing the margin of the slate to the Maryland 
line near Arnold's Mill. The limestone belt of the York Valley, lying on the N.W. of the slate, terminates 
near this spot in a wedge-shaped point, by the folding round of the overlapping middle secondary red sand- 
stone, which, after concealing the limestone, encroaches upon the slate. 

Prom the belt just described, which has its southern limit on the west bank of the river at Cline's Run, 
and on the east bank at Charlestown, we enter upon a limestone valley about two and a half miles broad. 
This somewhat corrugated basin constitutes the south-western prong or branch of the great Conestoga limestone. 
It tapers westward in a very slender folded belt, terminating in a point at the Eastern Branch of Codorus 
Creek; but it is extremely narrow only three miles west of the river, at the old Margaretta Furnace. It is 
quarried in two or three places near Cabin Branch Run. It contains a rather interesting stratum of somewhat 
coarse, calcareous conglomerate, consisting of lumps of grey limestone, imbedded in a dark slaty cement. This 
band is about one hundred feet thick, and occurs about a mile and a half above Beig's Mills. The furnace 
was supplied with ore from the northern margin of the slaty limestone at its junction with the Primal slate. 

At the river the limestone exhibits a high degree of metamorphism ; it is silicious and magnesian, 
imbedding thin layers of talc-slate and segregated quartz. The flexures, so far as they can be clearly made 
out, are gentle. The cleavage dips uniformly Southward at a high angle. 

The synclinal trough of altered Primal slates, embracing this fold of the limestone, somewhat expands to the 
S.W. and near the South Branch of the Codorus, or about a quarter of a mile west of the York and Baltimore 
Railroad ; and ten miles nearly south of York, admits another narrow trough of limestone. This rock is 
quarried on the farm of Mr Daniel Diehl. South-westward from Diehl's, towards Jeff"erson, it is excavated at 
several other localities, and converted into lime for the fields. At Christian KnuU's, east of Jofterson, we meet 
with iudications of iron-ore in it. 

We now enter upon that extensive area of barren rocks which first appears a little west of the Schuylkill, 
forms the southern boundary of the Chester Valley, and covers the southern portion of Lancaster and York 
counties. These rocks we are forced, after close study, to regard as constituting the base of the Primal system, 
though so altered as to have been hitherto mistaken for true Hypozoic metamorphic rocks of the Gneissic group. 
The reasons for this conclusion will be given elsewhere. They sustain the high table-lands through which the 
river flows, and constitute the rocky bed of the stream, above which the harder masses project, forming multi- 
tudes of little islands. Descending the river, the boundary shores approach each other, and their dark, wood- 
covered and rocky sides give to the scenery a wild and picturesque character. 

The precise line of contact of the limestone with the talcose slates is not clearly visible on the west side of 
the river ; indeed, there seems to be no line of sudden transition. The lower liands of the limestone, naturally 
more slaty than the higher strata, have themselves undergone so much metamorphism as to be scarcely dis- 
tinguishable from the Primal slates. 

For convenience in description, we shall first consider the belt of rocks included between the limestone on the 
N., and the mouth of the Conestoga on the S. The first and most notable fact is the great apparent unifor- 
mity in the direction of the dip, which throughout this entire distance is towards the N.W., varying from 15° 
to 45° W. of N. 

On the east side of the river the high table-land of Turkey Hill, formed of the rocks now under consideration, 
sends forth several spurs or fingers towards the East, all of which droop away only a few miles from the river, 
VOL. I. 2 A 



186 



PRIMAL ROCKS, SUSQUEHANNA RIVER. 



permitting the limestone to take its place at their extremities. These fingers are evidently of anticlinal 
structure. From examination of the Section, it will be seen that several close folds may be constructed from 
the dips in this belt. 

It is interesting to observe that the axis planes of these folds all dip towards the N.W. ; in other words, 
in a direction opposite to that which the Appalachian system of flexures usually observes. 

The cleavage throughout this belt is very distinctly defined. From the limestone to Green Branch Run, 
two miles below, it fliictuates from one side of the perpendicular to the other, but not more than 10° either way. 
Its strike is S. 50° — 60° W. The strike of the cleavage thus changes to S. 75° W. ; but approaching Lockport the 
planes of bedding become more conspicuous than those of cleavage, and in the flatter dips the scales of mica 
predominate in the bedding. The cleavage thus becomes less and less obvious, and at Lockport has entirely 
disappeared as a distinctive i^henomenon. 

Starting from the lower limit of the synclinal valley of Cabin Branch Run, which, on the eastern side of the 
river, is nearly coincident with the south bank of Wistler's Run, and examining the composition of the strata of the 
slate belt forming Turkey Hill and its extension westward, we may define the whole tract, as far as Lockport, to 
consist of the Primal slates under the condition of Micaceous, Talco-micaceous, and Gneissoid Schists of a pre- 
vailing greenish-grey hue. Throughout this space the north-westward dip exhibits no change to the S.W., 
but only varies its inclination, sometimes fluctuating suddenly as if from a close fold in the strata, but display- 
ing on the whole a progressive declension in its angle from an average of 75° or 80° on the northern side of the 
belt, to 30° as we approach Lockport. 

On the cleavage planes, which for the most part, as already stated, are very steep, we see in some places numer- 
ous small lenticular plates of segregated quartz. These obey the general law of parallelism to the cleavage 
structure, and not to the original bedding, and they afford an instance of that mode of molecular crystallisation 
of the elements of the rocks which, carried further, has produced, I conceive, the foliation or grain in aU mica- 
slates, gneiss, and other completely metamorphic rocks. 

Pursuing the line of section southward, down the west bank of the river, it will be seen that, passing Lockport, 
the mica-slates grow more gneissoid, or become more coarsely crystalline, with a more distinct development of 
their constituent minerals, and this semi-gneissic character prevails as far as Shenck's Ferry. In some portions 
of the mass, the folire of the mica-slate enclose plates of segregated quartz. The same dip which prevails above 
Lockport, continues to within a few hundred feet of Shenck's Ferry, the angle varying from 45^ — 20°, the 
direction N.W. Near the Ferry com.mences a series of low undulations, to be specified presently. As already 
intimated, the true cleavage structure disappears a little above Lockport, and therefore no portion of the belt 
now under review displays this phenomenon ; nor indeed do we meet with it, unless once or twice locally, 
anywhere to the S. of this neighbourhood within the broad metamorphic zone crossed by one section. This 
disappearance of slaty cleavage, and acquisition of a more highly crystalline structure in the rocks, is in strict 
accordance with that view of the origin of both, which ascribes them to a crystallising polarity among the 
mineral particles excited by a high subterranean heat, the difference between the slaty structure and crystalline 
foliation being merely the result of a difference in degree of the rearranging force among the mineral particles. 

A little more than half a mile below the dam near Lockport, there is a slender dyke of trap-rock visible, 
both in the canal bank and the river. It seems to dip steeply southward, intersecting the dip of the slates. 
This trappean dyke is very probably but a prolongation of the long curving injection of trap-rock which ranges 
from N. of the Conestoga, S.W. of Millersburg, and intersects the hills and valleys east of Safe Harbour, meeting 
the east bank of the river about a mUe above Shenck's Ferry. 

Passing now to the belt of country embraced between the vicinity of Shenck's Ferry and that of M'Call's 
Ferry, we find ourselves still in the same group of talco-micaceous schists occasionally gneissoid, which have 
been already passed over from above Lockport. Indeed, there is but little essential variation either as to aspect 
or composition in the strata throughout the whole wide tract passed over by the Susquehanna from the lime- 
stone vaUey of Cabin Branch Run to the slate belt of Peach Bottom or Slate Point, the chief change being to 
a more gneissic character between Lockport and Shenck's Ferry. 



M^CALL'S FERRY. 



187 



The special belt before us, or that from the Ferry to M^Call's, differs from the remainder of the region in 
containing several distiuctly-maiked broad undulations of the strata. There are, indeed, three anticlinal waves, 
all of which cross the Susquehanna towards the S.W. They are wide and flat, or show only gentle dips, the 
inclination on both flanlis being nearly equal. The first of these flexures is visible in the hill just north of 
Shenck's Feriy ; its dips are about 20°, the northern towards the N.W., the southern towards the S.W., showing 
that the wave itself is rapidly expiring westward. The next is a rather bolder, wider arch, occupying the whole 
breadth of the hill just south of the valley at the mouth of which the Ferry is situated. In this instance, 
likewise, both the N. and S. dips are deflected from westward, and at the very axis or summit of the wave the 
dip is nearly westward at an inclination of about 15°, that of the two slopes being about 20°. The valley of 
Shenck's Ferry is simply the synclinal trough formed by these two anticlinals. Some of the layers of talc-slate 
in the most southern of these anticlinals contain garnets. 

The third, or most southern, is a gentle broad wave occupying the hill, terminating on the river at. Duncan's 
Point. In it, the dips on both flanks of the arch are also nearly equal, not exceeding 15°. The whole anti- 
clinal, like the other two, sinks towards the West. 

The middle of the synclinal wave embraced between the last-named anticlinal of Duncan's Point, and that below 
Shenck's Ferry, is situated about two-thirds of a mile south of Otter Creek. Its S. dip is about 15°, its N. about 20°. 

In the south bank of Otter Creek, one hundred yards from the river, is situated York Furnace, near to which 
there exists a band of limestone, not more than two feet thick, enclosed between talc-slate. It is impure, 
and not suitable for a flux for the smelting of iron-ores, though the more compact portions might make a lime 
fit for agriculture should the bed be discovered thick enough to admit of being profitably quarried. It appears 
to be merely a calcareous layer in the talcose Primal slate, and not a fold of the Auroral limestone. 

Octahedral Iron occurs as a constituent of the talco-micaceous slates, in more or less development through- 
out the whole district, from Turkey Hill to Peach Bottom ; but it seems to be more than usually abundant 
between the vicinity of Safe Harbour and Shenck's Ferry. It occurs abundantly in minute but beautiful crystals 
near Cooper's Point, below Peach Bottom, not far from the State line. 

Purple Sulphuret of Copper, with a little blue and green carbonate of copper, enclosed in irregular veins of 
white quartz, were met with in excavating the canal at one of the deep cuts near Duncan's Point. These indi- 
cations of copper ore were, however, very faint, and there was nothing to imply the existence, either at this or any 
other locality along the river, of a possibly profitable lode of copper ore. 

Continuing our survey down the river, we pass over, between M'^Call's Ferry and Muddy Creek, very nearly 
the same class of micaceous schistose rocks already traversed higher up, the chief difi'erence being that they are 
somewhat more gneissoid and abound less in octahedral iron. Throughout this belt there prevails but one 
general southerly direction in the dip. This is at aU angles, from 20° near M'^Call's Ferry, to 50° in the vicinity 
of Muddy Creek, and is towards all points between S. 20° E., and S. 20° W., the former prevailing. This 
southerly dip continues, in fact, with one or two local interruptions, the whole way across the Slaty district, from 
the anticlinal at Duncan's Point to the zone of true ancient massive gneissic rocks and granite dykes south of 
the State Une. There can be little doubt, however, that this is not a genuine monoclinal belt of strata, but one 
containing many closely-compressed inclined foldings, the axis planes of which, if detected, would be found to 
dip at low angles southward ; for it is inconceivable that the strata here seen to dip so uniformly, should be of 
the enormous thickness implied by the supposition that they contain no flexures or repetitions of their outcrops. 
From the above-mentioned last visible anticlinal, to the first genuine j)lutonic or eruptive rocks, is a distance of 
at least eleven miles perpendicularly across the strike ; while the average dip is as steep as 45° or 50°. 
The data imply a thickness of seven and a half or eight miles. The supposition of so huge a depth of regularly 
sequent deposits, is incompatible with the well-ascertained comparative thinness of the whole formation on the 
Brandywine, and more remarkably still on the Schuylkill. 

But the existence of actual flexures, folded ones apparently, does not rest on inference ; it is established by 
observation, as the portion of our Susquehanna section below Muddy Creek will clearly show. That such 
compressed folds do thus repeat the same strata many times over at the surface, is plainly indicated hy a feature 



188 



PRIMAL ROCKS, SUSQUEHANNA RIVER. 



of the tract, well exhibited ou the ]Map ; I mean the running forward towards the N.E. of ridges and 
tongues of the slate, like that N. of Cabin Branch and Turkey Hill, into the limestone tract of Lancaster 
County, N. of its general southern boundary. These projecting tongues are but the terminations of the 
anticlinals which have thus lifted and spread out the slates below the limestone. When we follow this belt of 
metamorphic slates south-westward, through Maryland and into Virginia, this progTessive expansion at the 
sui-face, and from the cause here presented, becomes stUi more conspicuous. 

Returning to the special belt we have been describing, it will be seen by the section to exhibit much slaty 
cleavage or an abundance of foliation-planes. These fissures, seldom coincident with the planes of bedding, but 
for the most part steeper, dip like the bedding towards the S. Their prevaUiug inclination from ^PCall's 
to JNIuddy Creek, where the average inclination of the bedding is low, is as steep as 45°. From Miiddy Ci'eek 
southward, it is seen to become much steeper, untU, in the vicinity of Slate Point, it mounts to 80° or 85°. 
Below Hough's Run, S. of Slate Point, it ceases to be conspicuous. This prevailing southward dip of the 
cleavage-planes, coinciding as it does with the very general southward inclination of the strata, is certainly a 
striking confirmation of the law, several times already enunciated, of the parallelism of cleavage-structure with 
the planes of plication. To one convinced, as the author is, of the generality of this law, where the zone of 
cleavage-structure is a broad one, the phenomenon is of itself a satisfactoiy indication of the existence of a 
system of inclined foldings, even where the metamorphism has completely obscured these. 

The law here enunciated of the relation of cleavage to plication of strata, is not merely one of scientific 
interest, — it is of great practical importance, as every person may perceive who reflects that in districts really 
much convulsed, but which exhibit superficially but one direction of the dip, the miner or mineral explorer who 
might be deluded into costly outlays from the seeming imiformity and assumed depth of his mineral bed, wiU 
take warning at the indications which the cleavage may give him of shallow foldings and perplexing repetitions 
of the seams he may be pursuing. 

From Muddy Creek to the vicinity of Peach Bottom, the river intersects the same talco-micaceous schists 
seen above, but growing finer grained as we approach Peach Bottom. In this space there appears to be an anti- 
clinal flexure, the axis of which crosses the river a few hundred feet above the canal lock. 

Slate-belt of Peach Bottom. — The next subordinate belt which the section crosses, is the slate range of Peach 
Bottom and Slate Point. The rock here is a dark-blue indurated clay-slate, much of which has the structure of 
roofing-slate, extensive quarries of which have long been successfully wrought at the Peach Bottom Clifi's on the 
eastern side of the river, and also at numerous points west of the river, in York County, and in Maryland. The 
workable slate-belt here is about half a mile wide. The slaty cleavage and the bedding appear throughout to 
be nearly coincident in their dip, which at the quarries is nearly perpendicular a little southward. The quality 
of the Peach Bottom slates is veiy good, and their exportation is slowly augmenting. The belt runs north-east- 
ward through Slate Hill from the river, a distance of about two miles, and south-westward through York 
County from Slate Point, a distance of about six and a half miles to the State line. Slate-quarries have been 
opened N.E. of the river, along nearly the whole distance mentioned, but never extensively wrought, and in the 
same detached manner through York County. At Slate Hill on the river, the slate is quarried in steps or 
benches, and not in one general breast, though the material is so uniformly pure as to admit of being nearly 
aU wrought. On the east side of the river thei-e are seven quarries near the shore, and four others of smaller size 
back on the hills, which ai'e at the present time un-\vi-ought. On the York County side there is only one quarry 
at the river, but in the interior of the county there are seventeen more, embraced between a point two and a 
half miles back, and the end of the range six miles from the river. The workable slate appears not to extend in 
Lancaster north-east of the limit given, but in the other direction there are indications that it is prolonged beyond 
the distance of the six miles named. One of the quarries on the river. Brown's Lower Quarry, yields slates ^^•hich 
will bear strong stove heat without cracking, and the woi'kmen use flags of it for fr}'ing their meat upon. So 
uniform is the composition of the material, and so diffused and regular the metamorphism, that the original 
planes of sedimentation or bedding are too indistinct at these river quarries to be discernible. The cleavage- 
planes, the only \dsible ones, dip about 80° to S., 30° E., and this condition prevails throughout. 



SLATE OF PEACH BOTTOM. 



189 



Statistics. — During the year 1853 the quarries of J. and S. Brown yielded 1000 tons, and in the two pre- 
ceding years 1500 tons. Caldwell's quarry, on the same north-east side of the river, yields annually about 400 
tons. Cox's quarry, on the opposite side of the river, has aftbrded but a small amount ; but much slate is wrought 
in York County, where one quarry, that of Roland Perry, the largest in the belt, produced, in 1833, about 
2000 tons. 

The price of slate for the last six years has ranged between $li and $17 per ton. 

Slates of the largest size, of 24- by 1 4 inches, were $69 per thousand ; ditto 16 inches by 8 inches, $22 per 
thousand ; ditto 12 inches by 6 inches, $12 per thousand. 

In the extension S.W. of this general belt of Primal slates, there are five or more quarries wrought in 
Erederick County, Maryland, near the railroad eight miles from Fredericktown. 

The next belt of strata cut by the river, and indicated on our section, extends from below Slate Point to the 
second canal-lock below the State line, a distance of about four miles. The rocks here exjDosed are various 
forms of mica-slate and talcose-slate, alternating with talcose white sandstone, certain outcrops of which bear 
the unmistakable characters of the Primal white sandstone. One or two outcrops of chlorite-slate occur, and 
occasionally the mica-slate graduates towards a micaceous quartzose gneiss. Much of the finer-grained talcose 
slate is undistinguishable from rock, so-called, which near the Schuylkill, and along the South Valley Hill, both 
east and west of it, and also in the anticlinals of the Montgomery and Chester Limestone Valley, is seen in intimate 
alternation with the Primal white sandstone. Either from the more frequent presence in this district of the 
middle part of the Primal series, the White Sandstone group, or from a less excessive degree of metamorphism, 
the strata here exhibit a far lower condition of crystalline change than in some of the tracts further N., 
having fewer of the features of true micaceoixs schists, and more of the characters of genuine sedimentary sand- 
stone. Indeed, at several places between Slate Point and the State line, we meet with a rock which, in its 
composition, lamination, colour*, fracture, and whole lithological aspect, is absolutely undistinguishable from the 
main bed of the Primal white sandstone, as it is seen in Edge Hill and other notorious localities of this readily 
recognised rock. One of the localities is just below Slate Point, the sandstone forming, in fact, the soiith flank 
of the Slate Hill, and reposing, regularly bedded, immediately upon the slate itself, which near the contact is 
highly nacreous, and in that minutely wavy or crinkled lamination which usually denotes a metamorphism 
approaching the rock usually called Talc-slate. 

About 1700 feet further down the river, there is anotlier outcrop of Primal white sandstone immediately 
north of Hough's Run at the canal lock. Here the rock is between 90 and 100 feet thick. It dips at 
the canal level 45° to S., 30° E. ; but rising into the hill it grows flatter until it becomes nearly level, as if 
bending to form an antichnal arch ; indeed, it is difficult to resist the conclusion that these two South-dipping 
belts of sandstone are simply the two abutments of a wide fold or flexure, the northern flank of which is inverted 
into a somewhat steeper South dip than the southern. This view is confirmed by the crushed and contorted con- 
dition of the dark slates which fill the space between the outcrops of the sandstone. It is further confirmed 
by the presence in this neighbourhood, both within the supposed arch and at Slate Point above it, of a steep 
South-dipping cleavage, a feature quite usual in the slaty rocks throughout the district. 

At other points further down the river, especially between Rock Run and the State line, a material having 
all the aspect of the Primal white sandstone under a more extreme condition of metamorphism reappears. 
We meet it again, though materially more altered and crystalline, about two-thirds of a mile below the State line, 
and here, as we should expect, it is in contact with a dark crystalline slate, precisely such as we find the talcoid 
slates of the South Valley Hill, Chester County, where, in alternation with the sandstone, they are more than 
usually metamorphosed. In truth, we encounter repetitions more or less frequent and distinct of this altered 
white sandstone and its contiguous slates all the way along the river to the mouth of the first stream in Mary- 
land, more than a mile and half below the State line. In other words, we may recognise these outcrops of the 
Primal white sandstone throughout a belt nearly three miles and a half broad, from the south flank of the Slate 
Point Hill to near the crossing of the great belt of serpentine. 

Serpentine Belt. — Passing out of the talcose and micaceous slates which, as already stated, extend for about 



190 



PRIMAL ROCKS, SUSQUEHANNA RIVER. 



two miles below the State line, we meet a narrow belt of Serpentine rock having all the distinctive featui'es of 
the Serpentine of the southern border of Lancaster County, of which, indeed, it is but the prolongation. As in 
aU the other localities where tliis formation has been met -with, it is in contact with the talcoid or altered older 
Primal slates, immediately adjacent beds of which are frequently so impregnated with the magnesian mineral, 
and so changed thereby, as to seem at first sight like a stratified serpentine. Tliis rock contains much green 
actinolite. The full width of the dyke is not at present visible, but is is manifestly very narrow when com- 
pared with the space occupied by the belt under the State Une in Lancaster. Even here, however, its breadth, 
including the serpentinous slates associated with it, seemed at the time the canal was excavated to extend two 
hundred yards. Whether this slender outburst is connected with the extensive and broad tract of chromiferous 
serpentine barrens of Deer Creek in Maryland, or whether that is an independent and somewhat more southern 
range, we have not ascertained ; but it is notorious that the magnesian rocks abound extensively throughout this 
zone to the S.W. 

Almost immediately adjoining the outcrop of the serpentine at the river upon its south side, there is a 
slender band of gneissic chlorite rock. This is too imperfectly exposed to enable an observer to ascertain 
whether it is stratified or not, but the masses visible exhibit an indistinct irregular foliation, more suggestive, 
however, of slaty cleavage than of sedimentary bedding. 

Gneiss and Granite Belt. — The last subdivision of the ancient rocks traversed by the Susquehanna is a 
broad belt consisting mainly of massively-bedded gneiss under its several varieties, and of mica-slate and horn- 
blende slate cut by dykes of genuine intrusive syenite, granite, and greenstone trap. Perhaps the predominant 
rock of all is a thickly-bedded granitoid gneiss of the typical composition and structure assigned to that forma- 
tion. It consists, in other words, of the three characteristic minerals, quartz, felspar, and mica ; the quartz and 
mica predominant, and completely and widely detached, streaking the rock in fight and dark wavy bands and 
blotches. This is the rock which is so extensively quarried on the east side of the river, north, and also south, of 
Port Deposit, and used by the Federal Government for the Delaware breakwater and other national works. 
Besides this prevailing variety, there is a broad outcrop near Havre-de-Grace of a more felspathic granitoid 
Gneiss of a yellowish and pinkish tint ; it also is an admirable building-stone when large and coarse blocks of a 
durable material are wanted. Hornblendic gneiss, graduating into hornblende slate, likewise prevails. On the 
east side of the river, the southern limit of the crystalline rocks is one mile below Port Deposit, the shore faither 
south being Tertiary or Diluvium. 

Of the Intrusive Rocks, the principal varieties are syenite and granite, the former more abundant than the 
latter. Wide dykes of a fine-grained grey gi-anite are quarried near the canal about half a mUe above the old Cone- 
wango Bridge, and a little further north there is a thick dyke of white igneous quartz. These granite dykes dip 
steeply south-eastward. An augitic syenite displays itself in several thick dykes about two miles lower, and this 
and other varieties of syenite abound in the neighbourhood of the mouth of Deer Creek. Near the vein of 
quartz above the Conewango Bridge there is a dyke of greenstone, but tliis rock is not abundant along the 
river. Above Havre-de-Grace there are noble exposures of the yello\vish felspathic gneiss, not merely in the 
banks of the river but back upon the plain, where the edges of the strata are imperfectly covered by the attenu- 
ated margin of the horizontal tertiary sands and clays. Here the river, already a tidal estuary, expands into the 
Chesapeake Bay, the abrupt enlargement of which denotes the disappearance, deep below the ocean level, of all the 
older crystalline rocks, and the presence of the far more easily excavated strata of the uncemented and horizontal 
deposits of a tertiary or post-tertiary age. 

Reviewing the phenomena of cleavage throughout this southern zone of the Primal rocks as they are revealed 
on the Susquehanna, we discover an interesting exception to the prevailing law of a south-eastward cleavage 
dip, attended, however, with no interruption to the universal law of the parallelism of the cleavtige structure to 
axis planes of the flexures, or the direction in which the strata have been obliquely compressed. 

First, The northern tract of the Primal slates exhibits over their whole breadth, from the limestone near 
Wrightsville to the limestone of Cabin Branch Run, the normal or south-eastward dip, and under conditions 
which imply at least two anticlinal folds with axis planes, dipping, of course, to the same quarter ; and through- 
out this belt the cleavage fissures invariably dip at a steep angle in the same normal du-ection. 



CLEAVAGE. 



191 



Secondly, The wider middle tract between the synclinal of the Cabin Branch Run and the anticlinal district 
of Shenck's Ferry, displays, with scarcely any interruption, an abnormal or north-west dip of the strata ; but 
here the cleavage is nearly vertical, sometimes very steeply southward, but more prevailingly northward, or in the 
direction approximating to parallelism with the steep abnormally-dipping axis planes. This is the state of 
things from a little S. of Cabin Branch Eun to the vicinity of Lockport, where the cleavage, previously fading, 
disappears. 

Thirdly, Crossing the narrow belt of more open and visible anticlinal waves, between Shenck's and 
M'^Call's Perries, we enter, above the latter locality, upon one great sequence of south-east dijDS of the sti-ata, 
extending the whole way to the State line, and indeed to the southern limit of the metamorphic rocks at the 
mouth of the river. From M'^Call's Ferry to Slate Point the section presents us with a third zone of cleavage ; 
but this observes invariably its normal direction, dipping to the S.E.,.and, as usual, at a steep angle. Below 
Slate Point, where the degree of metamorphism, even in the Primal slates, becomes once more excessive, the 
cleavage again vanishes, or gives place to that condition which is called foliation, and which does not permit, 
except in rare instances, the distinct recognition of the original lamination of the strata. 

It would thus appear that even where the cleavage assumes an abnormal direction of dip, it is in obedience 
to an equally abnormal diiection in the plication of the strata ; and we may further remark, that wherever the 
rocks exhibit evidence of excessive metamorphism, or, in other words, show an approach to the maximum con- 
ditions of crystallisation or separate segregation of their constituent minerals, the cleavage ceases, and foliation, 
or that structure which is derived from the parallel arrangement of the component crystalline minerals, takes its 
place. 

PEIMAL SERIES, OR SLATE-BELT IN THE SOUTHERN PART OF YORK COUNTY. 

As already intimated, very little need be said in detail of the altered Primal slates S.W. 
of the Susquehanna in York County, no connected section being possible after leaving the bank of 
the river. Even on the line of the York and Baltimore Railroad, the natural and artificial sections 
of the rocks are infrequent, and so shallow that it is not possible to trace out the changes in the 
dip of the strata, detect their foldings, or recognise their lines of contact. As the Susquehanna 
section furnishes a far more complete exhibition of these, it will suffice to say of the western half 
of this slaty belt, that quitting the range of the synclinal limestone trough called the York 
Valley, and proceeding southward by the Codorus Creek and its South Branch, we cross nearly 
at right angles to the strike a wide succession of bluish-grey fine-grained micaceous and talcose 
slates intimately set with cleavage planes, the flakes of mica being invariably arranged upon 
the cleavage surfaces. Some bands of a very pale or whitish green tint are extremely silicious, 
with delicate micaceous and talcose partings, and are identical in aspect and composition with 
the highly -altered and shaly portions of the Primal white sandstone of the vicinity of the 
Schuylkill, for example, at Barren Hill. As far S. as the Hanover Junction, the apparent dip of 
the strata is steeply southward ; though within this space there are indications, especially 
between the third and fourth mile-posts on the railroad, of an anticlinal flexure in the strata, 
broad and low, corresponding very* nearly with one of the flexures in the same slate-belt at the 
river. The cleavage-dip likewise agrees with that at the Susquehanna, being everywhere south- 
ward at a high angle. These conditions imply one or more flexures of the prevailing character, 
steep or inverted on the north-west side, extending to the synclinal trough or little valley just 
S. of the Hanover Junction, which appears to be seated in the basin which embraces the lime- 
stone belts of Cabin Branch Run and of Jeff"erson. Passing S. of this natural boundary, ,W6 



192 



PEIMAL EOCKS, YORK COUNTY. 



enter at once on a succession of ex^^osures of micaceous slates, very similar to those traversed by 
the section further north, with the exception that they are more crystalline. These continue with a 
steep north dip as far as the village of Glen Rock. There the strata begin to assume a more highly 
metamorphic character, and lithologically would be called green quartzose micaceous gneiss, or 
gneissoid mica-slate, and they retain this crystalline type the whole way hence to the State 
line. It is worthy of note, that the northward dip seen in the district north of Glen Eock con- 
tinues, with only local interruptions and trivial contortions, throughout the remaining part of 
tlie section. It i^ toward the central portion of this more gneissoid division, especially in the neigh- 
bourhood of the Shrewsbury Station, about three miles by railroad north of the State line, that 
the contortions or little flexures most predominate ; and it is interesting to observe that these 
correspond very nearly in their latitude of transverse distance across the slate-belt, with those 
noticeable at the Susquehanna, in the vicinity of Otter Run. Another circumstance harmonising 
the two sections, is the absence of any distinctly-pronounced South-dipping cleavage after we 
pass the village of Glen Rock, but in place of this a wa\y foliation seemingly coincident with 
the stratification. The section at the State line does not enter the belt of South-dippiug stratifi- 
cation, with steeper South-dipping cleavage, which the Susquehanna Valley exposes from M"'Call's 
Ferry southward the whole way to the serpentine belt at the State line. 

Reviewing these facts of dip and structure, we find in this comparison of the two sections, a 
striking confirmation of the general principles of the relations of cleavage to the crust undula- 
tions so frequently enforced in this work. The whole topographical geology of southern 
Lancaster aud Yoi-k demonstrates a progressive sinking of the flexures, or anticlinal and synclinal 
waves, as they advance north-eastward to the Susquehanna, and across it to the limestone tracts 
of the Conestoga and Pequea, where the slates finally sink out of sight in flattening anticlinal 
spurs. Now it is iu this district of subsidence, or at the Susquehanna, in the belt prolonged from 
Tm'key Hill, tliat the cleavage-dip approximates to the perpendicular, leaning almost as often 
to the North as to the South, parallel to the axis planes of the flexures, many of which, as already 
intimated, observe a northward instead of a southward dip. Fvirtlier towards the S.W., where 
the flexures are manifestly more closely compressed, and therefore more oblique, but where 
their axis planes, in place of dipping to the south-eastward, descend north-westw'ard, contrary 
to the usual rule, the cleavage is less perpendicular and more constantly towards the same 
abnormal quarter. 

In a rather wdld and sequestered neighbourhood among the Barren Hills, thirteen miles 
S.E. from York, we come upon Susan Ann Furnace, not recently in operation, but undergoing 
repairs. The iron ore procured near it was found to make an inferior metal, and was abandoned 
for a purer variety obtained about seven miles to the W., at a point seven and a half miles S. 
of York, where the mineral occurs between seams of disintegrated slate, in nests and loose 
deposits. It is rather silicious, but is said to yield a tolerably good iron. Near the Maryland 
line, at Essex Hall, on the farm of Mr Clark, a small deposit "of iron ore Avas worked some years 
ago. In the fields between this and the State line, are found loose crystals of red oxide of 
titanium. 



CHIQUES EIDGE. 



193 



CHIQUES EIDGE. 

A broad and conspicuous chain of hills, known as Chiques Ridge, is the next principal belt 
of the Primal strata. It originates about three miles N.W. of Lancaster, and after ranging 
almost due northward for eight miles, crosses the Susquehanna a little above Columbia, and extends 
parallel with the southern side of the river, until it passes Codorus Creek, and is overlaid by the 
south-eastern edge of the Mesozoic red sandstone. This belt is in many parts more than one 
mile in breadth, and near its eastern extremity, where it is widest, it contains two or three 
anticlinal flexures. 

The general structure of this ridge, as seen at the Susquehanna, is that of a very much com- 
pressed or folded anticlinal flexure, on the northern side of which the strata lie in an invei'ted 
altitude ; that is to say, the rocks, originally uppermost, are seen dipping apparently beneath 
others inferior to them in the order of stratification. The consequence is that the limestone 
lying N. of the ridge dips southward, to underlie the rocks of the ridge. Above the bridge 
at Wrightsville, the most southern member is a slaty sandstone evidently one of the upper strata. 
It dips 70° S. Approaching the main axis of the ridge, we meet high perpendicular cliffs, 
consisting of the Primal White Sandstone, and indurated Primal upper slates. The colour of 
the rock is whitish, sometimes of a bluish tinge. About a mile below the mouth of Codorus 
Creek, to the N. of the folded axis, the sandstone is underlaid by a tolerably thick belt of striped 
slates, this again by a succession of thick strata of sandstone and slate, the latter predominating, 
until we reach the limestone at New Holland. Sometimes the slates dip slightly N. from the 
axis, and sometimes they are inverted, or dip towards it. Half a mile above the furnace on 
Codorus Creek, the compact white sandstone dips N. 60°. From this to Brillinger's, we see 
no more of the sandstone, the rock being the upper silicious slate similar to that at 'the mouth of 
the Codorus. The belt of white sandstone terminates westward at a point at about two miles 
N.E. of York, w^here the Codorus flows round it. The belt of silicious slate, lying further 
N., passes westward from the mouth of the Codorus and New Holland, ranging S. of Liverpool, 
until it is covered by the red sandstone at Shultz's, four miles north of York. 

At Chiques, on the Susquehanna, we have a very distinct and bold exposure of nearly all 
the Primal strata of this belt, as shown in the enlarged section. 



SECTION TEOM COLUMBIA TO THE CHIQUESALUNGA CEEEK AT HALDEMAN'S, 

THEOUGH THE CHIQUES EIDGE. 

This fine natural section gives us a view of the whole constitution ami structure of the Chiques Ridge. By 
it we learn the precise conditions into which the strata have been altered by igneous agency. The rocks 
embraced here are in the descending order, or that in which, looking eastward, we shall leview them. 

1. The alternating or passage l:)eds of slate and limestone, connecting the bottom of the great Auroral lime- 
stone series with the top of the Primal ; 2. The Primal newer or upper slates ; and, 3, The Primal White Sand- 
stones. 

1. The alternating group extends from the town of Columbia, past the railroad engine-house to the furnace. 
Between the street at the engine-house and the furnace, a distance of about 1100 feet, we cross two thick bauds 
of the limestone and an interposed bed of slate, all dipping at an average angle of 50° to the S.S.E. The first 
bed of limestone, magnesian in its composition, is exposed for a little more than 2.30 feet in the bank. It is 
VOL. I. 2 B 



PRIMAL ROCKS— CHIQUES RIDGE. 



veiy crystalline, mottled, and partially intersected with steep South-dipping cleavage fissures, and altogether 
exhibits evidence of much metamorphism ; indeed, the cleavage in i)laces renders the recognition of the bedding 
quite obscure. 

The band of slate, also about 250 feet across, is of a duU olive-colour, very ferruginous, highly indurated, 
and intimately cleft with cleavage-joints. These dip about 75° southward, or steeper than the strata do ; nor 
do they coincide in strike with the bedding, but range more E. and W. 

Passing the slate, the hist or lowest band of the limestone is seen exposed for about 400 feet. This is also 
highly magnesian, but more sandy than the other bed. It is quite as highly altered, being crystalline, white 
and mottled, and full of cleavage. 

2. From the furnace to the first exposure of the Primal sandstone, a little north of the second ravine, there is 
a fine natural section of the whole thickness of the Primal upper slate, though very possibly a folded flexure 
near the Tunnel may repeat a portion of the beds under three parallel dips. The apparent dip is monoclinal 
until we pass the second ravine, where a low narrow anticlinal wave is discernible. If we assume no fold or 
repetition of the strata between the furnace and the ravine, a distance of 2500 feet, and accept 45° as the 
average dip of the beds, Ave must suppose the thickness of this upper Primal slate to exceed 1800 feet ; a bulk 
far exceeding that which it possesses further eastward in the North Valley Hill of Lancaster and Chester. 

This slate apjjears to be even more transformed in its texture by igneous action than the beds above it. It 
is very hard, internally of an olive green, externally of a dingy brown, from presence of much oxide of iron, and 
lias a baked aspect. It exhibits, moreover, in every part of the mass, an excessive amount of the cleavage 
fissures. These dip in all cases southward, and at angles varying from 80° to 65°, declining as we go north- 
ward towards the anticlinal flexure in the underlying Primal sandstone, wdth the axis plane of which those 
most adjacent ai'e almost strictly parallel. Even in the low small arch N. of the second ravine, the cleavage 
planes are true to this law of parallelism, unaffected by any tendency to the fan-tail arrangement which such an 
arch would have induced had it been more remote from the overpowering influence of a great folded flexure. 

3. Passing the base of the upper Primal slate, we cross next an irregular oblique arch or anticlinal fold of 
the Primal sandstone, occupying a width of about 500 feet. The southern flank of this arch contains two 
gentle waves ; the northern is completely inverted, so that the sandstone beyond the axis dips almost parallel 
with that south of it. Between these two similarly inclined legs of the curve, a mass of slate, about 150 
feet across its strike, displays itself in the very axis of the flexure. This is manifestly the uppermost bed 
of slate of the Primal sandstone group ; this formation here containing as its chief members two white sand- 
stones, and an interposed bed of slate about 300 feet in thickness. Between the anticlinal axis, lifting this 
middle slate to view, and the northern base of the Chiques Ridge at Haldeman's, a distance of nearly 3000 
feet, occur three other exposures of the Primal white sandstones : the first of these is some 250 feet above 
the Henry Clay Iron- Furnace ; it is the same sandstone as that of the compressed anticlinal just passed over, 
here brought again to the surface with a southern dip of 60°. Between it and the anticlinal fold there is there- 
fore an oblique compressed basin of the lower members of the upper Primal slate, at least such is a reasonable 
construction of the strata as they are seen. The slates embraced in this supposed synclinal trough show the 
slaty cleavage dipping 70° to S., 20° E. ; whereas the planes of stratification dip at 60° to S., 10° E., a deviation in 
strike of 10°. 

This upper sandstone of the Primal sandstone group has, at its outcrop N. of Henry Clay Furnace, a 
thickness of about 27 feet. 

The slate, or middle member of the same group, about 300 feet thick, as already stated, next rises, leaning- 
southward at an angle of 50°, and immediately beyond it there appears the upper portion of the lower or main 
Primal white sandstone, most curiously doubled into a beautifully-rounded oblique saddle, the north side of 
which is perpendicular, the south dipi^ing at 50°. It rises above the level of the road about 20 feet, and con- 
sists wholly of the white silicious sandstone, without joint or fracture, or trace of cleavage fissure, and with 
the lines of original bedding only barely discernible. Here the pure massive sandstone has undergone 
a most excessive, yet regular folding, or doubling together, at a time when the materials must have been 



PIGEON HILLS. 



195 



in a partially movable or semi-plastic state. It is one of the most striking instances visible within the whole 
Appalachian Chain, of this plasticity of the sedimentary matter of the ancient Palaeozoic strata. The slaty mass 
overlying this much bent and compressed sandstone, has been doubled into a much more acute curve at the 
anticlinal axis, and is, moreover, greatly cut in the sharp synclinal fold, just N. of the anticlinal, by cleavage- 
joints. Indeed, all the beds from this middle anticlinal sandstone to the third or northern one, are pervaded 
with the cleavage fissures : those in the slate, separated by very short intervals ; those in the beds of sandstone 
occurring at an average distance of about half an inch. 

Approaching the third anticlinal, or that of the main northern crest of the ridge, we meet the lower or chief 
member of the Primal white sandstone group, elevated in a gi'and waving arch, forming a superb mass of cliffs 
south of and behind the mansion of Professor Haldeman. Pacing the ends of these strata, which span in all 
a distance of about 1000 feet, we discover that the sandstone exhibits, when closely scrutinised, not a sym- 
metrical, normal wave, but one containing two synclinal curves upon its crest. The southern flank of the 
general wave dips southward at a gentle angle, increasing from 30° to 45°. The northern flank plunges from 
the last rapid turn, almost perpendicularly out of sight, to fold most probably backwards beneath the arch, and 
finally to abut, with dislocation, at a depth of 2000 feet or more against the south-dipping limestones visible 
just beyond it in the stream. 

In this main terminal arch the cleavage, which elsewhere dips invariably southward, deviates from this 
prevailing rule at one point on the S. slope of the wave, and dips at a steep angle northward. Elsewhere 
throughout the flexure it slants southward at an angle of 80°. 

The thickness of the lower sandstone member cannot be accurately estimated, but, including its thin beds 
of slate, we may assume it at not less than 300 feet. The fault or dislocation alluded to evidently extends a 
great distance E. and W. along the northern base of the Chiques Kidge. Some of the beds of the middle and 
lower members of the Primal white sandstone exhibit, in the Chiques Ridge, a great multitude of specimens of 
the stemlike fossil, the Scolithus linearis. This is nearly straight, and would seem to have a small knob 
or swelling at one of its terminations. Its position in the rock is invariably perpendicular to the plane of the 
beds, and therefore where cleavage disguises the direction it is a good guide. 

Pigeon Hills. — About eight miles soutli-westward from York there occurs the range called 
the Pigeon Hills, rising through the limestone of the York Valley. These hills have an elliptical - 
form, are between seven and eight miles loDg and three broad, terminating south-westward near 
the turnpike, at a point four miles north of Hanover. The strata comprising different portions 
of the Primal sandstone and Primal newer slate, consist usually of a dark slate and a light- 
coloured sandstone, of different degrees of fineness and compactness. The whole belt, though 
carefully ex]3lored, develops little of interest in a scientific or an economical point of view. 
About four miles N.N.E. from Hanover, occur greefi chlorite, and a beautiful variety of foliated 
oxide of iron. The slate in the neighbourhood shows small traces of copper ore. A belief exists 
throughout this neighbourhood that the slates of these hills are of the coal formation, and that 
coal perhaps exists in them, whereas they belong to the very lowest fossiliferous formation of 
our State ; while the workable coal is exclusively confined to a wholly different group of rocks, 
lying much higher in the order of stratification, and occupying an entirely different geographical 
range. 

The junction of the slate and limestone rocks is seen on the S. of the Pigeon Hills, about four 
and a half miles N.E. from Hanover. 



CHAPTER IV. 

PEIMAL ROCKS OF THE SOUTH MOUNTAINS BETWEEN THE DELAWARE 

AND SCHUYLKILL. 

That the Primal series is not continuous in the belt of the South Mountains, where they 
traverse Northampton and Lehigh, is rendered highly probable by the infrequent and local 
manner in which it shows itself. Still we are entitled to consider it as not confined merely to 
the few scattered points where it emerges to the day, but as resting in many places at the base 
of the Gneissic ridges, buried under a deep covering of loose Diluvium. I shall hereafter refer 
to various places where it rises to the surface in sketching the limits of the limestone, which, 
whenever it is present, it immediately underlies. There are many exposures in this part of the 
chain where the limestone is seen resting directly in contact with the gneiss. At the Delaware 
the Primal sandstone flanks the gneiss in the Lehigh Hill, and also near Durham. Going west- 
ward, it shows itself on Durham Creek, a little E. of Springtown, in the ridge bounding the 
limestone E. of Hellertown, and in the end of the spur immediately E. of the South Branch 
of the Saucon. Ascending the Lehigh, the first point where it appears in place is on the south 
side of the river about a mile S. of the Bethlehem Bridge, where it occurs in a thin band, 
resting on the gneiss, and dipping northward 20°. It runs in a narrow belt from the road east- 
ward to the Saucon, where it adjoins the lower termination of the limestone of that stream. The 
sandstone occurs on the northern slope of the small ridge of gneiss rocks occupying the north 
side of the Lehigh, E. of Allentown. It shows itself again not far from this, on the southern 
side of the river, about a mile below the Allentown Bridge, the piers of which have been con- 
structed of it. Here it constitutes but a thin stratum, the limestone in some places lying nearly 
in contact with the gneiss. There are but two other localities in Lehigh and Northampton 
counties. The first of these is near the top of the mountain E. of Emaus, where a rather coarse 
variety of the sandstone is seen dipping with the slope of the mountain, rather steeply towards 
the W.N.W. The mountain itself is Gneiss. The other locality is at Millerstown, and exhibits the 
sandstone as a low ledge at the foot of the mountain, dipping 10° towards a point 75° W. of N. 
Westward of this, especially in Berks, it increases in thickness and abundance as we approach 
the Schuylkill. 

In Berks County the white sandstone, which appears in a few detached localities along the 
north-western line of the South Mountains in Lehigh County, begins to show itself as a more 
continuous formation, rising even into high irregular ridges in the south-western part of the 
chain. A very usual position of the sandstone is upon the flanks and around the extremities of 
the spurs of the gneiss, where it often indeed overtops the crystalline rocks, which then appear, 
only on the crest of the hills as low dykes difficult to trace. Even where the sandstone is best 
developed, some difficulty attends our tracing it as a continuous formation. This arises from its 
immediate proximity to the greatly-convulsed gneissic strata, and from its lying so frequently 
on the declivities of the hills, where its outcrop is much obscured by fallen fragments. The 
sandstone, where it is subordinate to a larger ridge, often either encircles, at a little distance, the 



LEHIGH AND BERKS. 



197 



extremity of the spur, or lies more or less obliqviely across it. Sometimes, even in the middle of 
a high track of the sandstone, where no regular belt of older rock protrudes itself, evidence is 
perceived that this has reached the surface at certain spots, from the quantity of angular frag- 
ments. The sandstone itself offers often great difficulty in determining its stratification and the 
true direction of its dip ; whole hills looking like mere piles of huge angular blocks, innumerable 
fissures and cleavage-joints traversing the beds so as greatly to perplex the observer. 

Passing from Lehigh into Berks, the first exposure of the sandstone is at a hill lying S. of 
the Little Lehigh, and about two miles S.E. of Metztown. Here the rock is chiefly in loose 
pieces, covering the foot and lower declivity of the hill. The sandstone also shows itself in place, 
about one mile S. of Metztown, immediately W. of the church. Between the visible edge 
of the limestone, which passes by Metztown and the foot of the hills further S., there is a 
considerable tract of country where no rock appears upon the surface, with the exception of the 
isolated tract of sandstone at the church just referred to ; a deep covering of diluvium hiding 
everything from view. Approaching the mountains from the N., the first rock seen in place 
is a white variety of gneiss. This is on the road leading to Hoof's Inn. West of this, in Maxa- 
tawny Township, the limestone is seen where a road crosses the Sacony Creek. The sandstone, 
which shows itself N.E. of the creek, disappears a little S. of Grim's Mill, the gneiss showing 
itself on the W. side of the stream, between the mill and Hunter's Furnace. 

The general margin of the limestone passes about a quarter of a mile N. of Walnut-town. 
About a mile south of this place, to the N.E. of the road, occurs a sandstone ridge, running in a 
N.E. direction. A little further S., upon the same road, we observe the outcrop of the gneiss. 
This gneiss, part of a long belt, averaging about a mile in breadth, terminates at Miller's Mill on 
Dry Eun. A belt of the sandstone, as already described, flanks it both upon the N. and S., 
the sandstone uniting round the point of the gneiss, a little east of Solomon's Temple. South- 
ward from this last-mentioned place, towards Reading, the sandstone lies on the E. of the road 
the whole way to within three miles of the town, where a belt of slate, the uj^per member of the 
Primal series, crosses the road. If wo here turn aside to the N.E., taking the road to Barnard's 
Mill (Rothermel's Mill on the county map), we encounter, just at the mill, a low protruding mass 
of igneous rocks. A little to the N.W. of this point, a small body of limestone has been dis- 
covered, S. of which, in the sandstone, we may trace a low dyke of syenitic rocks running 
towards the N.E. E. of its north-eastern end, and W. of its south-western, occur two 
other small patches of limestone. The line dividing the limestone of the Schuylkill Valley 
from the sandstone and slate bounding it on the E., after following the road which leads from 
Solomon's Temple south, suddenly cm^ves to the eastward about two miles north of Reading, 
reaching, but not crossing, the road from that city to Pricetown. Here, at Rothinberger's Inn, 
turning very abruptly to the S.W., and gradually receding westward from the road last mentioned, 
it next runs to the Schuylkill, passing through the western side of Reading, leaving thus a 
triangular tract of the limestone included in the general area of the sandstone. 

Hills East of Reading. — ^Penn's Mountain, commencing E. of Reading, and running in a 
N.N.E. direction nearly five miles, consists, on its summit and western side, of the Primal white 
sandstone, dipping to the W.N.W. Descending the eastern slope of the mountain, we soon 
encounter the gneiss rocks, which maintain this position as far to the S.W. as Kesler's Mineral 
Spring. This is the termination of the wide belt of gneiss and syenite, coming ofl" from the general 



198 



SOUTH MOUNTAINS EAST OF THE SCHUYLKILL. 



chain with a prevailing south-west and north-east direction of the strata. At Spie's Church there 
occurs a high sandstone ridge in the midst of the gneiss, being detached from any other tract. 
Penn's Mountain, at its northern extremity, sweeps suddenly to the eastward, jutting between the 
main belt of the gneiss around Spie's Church, and a narrower tract which crosses the Eeading and 
Pricetown road. N. of this last tract, and N.W. of the prolongation of Penn's Mountain, are 
some high sandstone ridges, probably concealing dykes or beds of crystalline rocks between them. 
Pursuing the road north-eastward to Miller's Inn, we have the sandstone on the N.W., while on 
the S.E. the hills consist principally of gneiss. Between Millers Inn and Pricetown the road separ- 
ates a hill of gneiss on the S.E. from a high short ridge of sandstone on the N.W. Gneiss occurs 
also about one mile from Pricetown, south-east of the road going towards Sterner's Inn (of the old 
State map). A sandstone ridge rises at Sterner's Inn, on the north-west side of the road, and extends 
nearly to the tributary of Manatawny Creek, in Rockland Township, beyond which, until we pass 
Roth's MiU,all the rocks are crystalline. Going E. of S. from Roth's Mill to Pine Creek, we encoun- 
ter none but gneissic rocks forming a wide tract. The sandstone, however, shows itself at the 
spot marked Shiffert's Inn on the county map, appearing on the slope of the hill N. of the road. 
The rock here is somewhat coarse and of a purplish colour. Passing to the S.W. it seems to cross 
the road. Descending the creek we meet another ridge of similar sandstone, occupying the west 
side of the stream, at a mill designated on the Map as Mineder's. Further S., about a quarter 
of a mile N. of Snyder's Upper Forge (Udree's Forge of the old map), the sandstone again shows 
itself on a small hill E. of the creek, and again on its W. side. 

The hill immediately to the S.E. of Sterner's Inn consists obviously of gneiss, the surface 
being wholly covered with their fragments, though no regular outcrop is seen. Still pursuing 
the road to Oley Furnace, we pass diluvium, containing much fragmentary sandstone, until at the 
creek, close to the furnace, we behold the sandstone in place, dipping steeply on the east side of 
the stream to the N.N.W. The rock here is coarse and reddish, and occasionally very talcose. 
Immediately W. of the creek lies a large hill of syenite, and about half a mile nearer Fredens- 
burg, we come upon the margin of a wide tract of slate, apparently the upper member of our 
Primal series, of which the sandstone hitherto most commonly encountered is the lower. Nearly 
two miles N.W. from Fredensburg, on the north-east side of the road to Miller's Inn, occurs a belt 
of sandstone, dipping steeply to the N.N.W. Here is an old mine of iron ore to be described here- 
after. Beyond this a sandstone ridge is seen running parallel with the road, about a quarter of 
a mile on its north-east side. Between this and Miller's Inn, an interval of about a mile, the 
prevailing rock is gneiss. 

Let us now trace the line which divides the gneiss from the Primal slate and sandstone, and the 
Auroral limestone in the northern and western parts of Oley Township. About three-fourths of a 
mile S.W. of Lobach's Mill, on Pine Creek, we come upon the margin of the limestone, crossing 
the stream in an eastern and western direction, through the lands of Jacob Keim. The dip here is 
due S. 60°. To the N.E. and E. of this the sandstone shows itself in a belt, to be presently described. 
North of St Peter's Mill (marked Maul's on the old map) runs the edge of the gneiss, which here 
exhibits no sandstone interposed between it and the limestone. The margin of the limestone 
is well seen half a mile W.S. W. of the mill, the rock dipping steeply to the S.S.E. Immediately 
above this limestone, on the creek, we have the slate crossing the stream just at the road leading 
to Sterner's Inn. The true dip of this last rock is difficult to discover, owing to the obscmity of 



HILLS EAST OF KEADING. 



199 



the divisional lines of the strata, and the abundance of cleavage planes, wholly independent of 
the lines which mark the dip, the dubious direction of which leads to some uncertainty respect- 
ing the precise formation to which the stratum belongs. Could its beds be seen passing unequi- 
vocally under those of the limestone, it would plainly prove itself to be the Primal newer slate ; 
if, on the other hand, it shoidd be seen to dip away from the limestone at the line of contact, no 
doubt would remain as to its being part of the Matinal slates. The margin separating the slate 
from the gneiss passes about half a mile N.W. of Fredensburg. Taking the road leading out of 
Fredensburg to the S.W., we pass over the slate for nearly a mile and a half, until we cross a 
little stream, the dividing-line of Alsace and Oley townships, where we pass directly upon the 
gneiss. Ascending the creek by a steep ravine, we pass the eastern termination of the spur of sand- 
stone at Spies Church, already spoken of East of this spot the boundary of the slate and gneiss 
is near Knabb's Mill (Reiff's on the old map). The hills immediately W. of the mill (marked 
Knabb's on the map), and of the road separating Oley and Exeter townships, are strewed with 
fragments of gneiss, as far down the creek as the first exposure of the limestone, which is half a 
mile north of the road running westward from Oley Forge. Following this road, which deflects 
towards the S.W., we pass across a corner of the limestone tract, and at a short distance W. of 
the Manokesy Creek encounter the common margin of the limestone and the gneiss. These two 
formations rest apparently in contact, from the upper point of the limestone, on the Manokesy, 
below the mill marked Knabb's, throughout a mile and a half towards the S.W. 

About two miles E. of Maurer's Inn, the sandstone shows itself in place, between the lime- 
stone and the gneiss, on the southern slope of a hill, some distance N. of the church. Under 
this sandstone is an argillaceous slate, probably the Primal older slate, in very thin laminae. 
Between this and Maurer's Inn the rock is exclusively sandstone, the large double hill N.E. of 
the tavern being entirely of this formation. Here a quarry has been established for getting 
building-stone ; the dip of the rock is obscure. This ridge 'of sandstone extends in a north- 
easterly direction, about two miles and a half towards the insulated sandstone hill, near Spie's 
Church, from which, however, it is separated by more than a mile of gneiss. East of the ridge 
the rocks are a white variety of gneiss, consisting of quartz and decomposing felspar, and a 
syenite composed of felspar and hornblende, in frequent alternation with the gneiss. Where 
these rocks abound the surface is marked by small rounded hills, covered with fertile soil, giving 
a pleasing aspect to the country. A similar topography is particularly striking in some parts of 
Colebrookdale Township, hereafter to be mentioned. 

The limestone belt, bounded, as we have already said, for the first mile and a half by gneiss, 
runs afterwards the whole way to the Schuylkill, below Reading, crossing Bishop's Creek about 
a mile below Maurer's Inn, and folding round the southern point of the Neversink Hill. From 
the Manokesy, westward to the Schuylkill, the limestone belt, bordered on the S. by the 
middle secondary rocks, contracts into a narrow zone, a few hundred yards in breadth. On its 
narrow limit it dips to the S. Where it crosses the Perkiomen turnpike, three miles from 
Reading, it shows in a quarry near the road many beds of a crystalline granular structure. Much 
of the rock at this place is of a dull yellowish white. It dips a little W. of S. It strikes the 
western reach of the Schuylkill, about a mile and three-fourths S. of Reading, where it is 
overlapped on the S. by the coarse calcareous conglomerate of the Middle Secondary series. 
North-eastward this narrow belt opens into the wide tract of limestone, which occupies much of 



200 



SOUTH MOUNTAINS EAST OF THE SCHUYLKILL. 



the eastern half of Oley Township. From its southern point on Manatawny Creek, a fourth of a 
mile below the line dividing Amity from Earl townships, the • eastern edge of this large tract 
passes up the Manatawny, and then up its eastern tributary, as high as the line which separates 
Oley from Pike. Its northern margin crosses Pine Creek, about a mile below Lobach's Mill. Its 
north-western corner is at the place marked on the map, Peter's Red Ochre Mine. Its western 
limit is the eastern boundary of the slate, which occupies a large tract in the western half of 
Oley. The limit between these rocks runs southward, nearly through the middle of the town- 
ship, until it strikes the Exeter line a little E. of Manokesy Creek. 

The slate, which we have already mentioned to be most probably the Primal newer slate, 
spreading from the western edge of the township (Oley), eastward beyond Kemp's Inn, shows 
generally a dip to the S.S.E. About half a mile S. of Kemp's Tavern the slate is bordered by 
slaty limestone, which apparently overlies it. The slate E. of Fredensburg graduates into slaty 
sandstone ; but S. of Rieff's MiU the slate is soft and sectile, approaching in texture to pipe- 
clay. At this and several other places its strata are intersected by veins of quartz. 

I have already referred to the belt of sandstone which occupies the valley of Pine Creek. This 
extends from the neighbourhood of Pott's Forge to the edge of the limestone, a mile below 
Lobach's Mill, where, doubling round the point of a wide spur of the gneiss, it runs eastward, to 
join the much longer tract of sandstone which follows the Manatawny and its eastern tributary 
in Pike Township, for many miles. This latter range of the sandstone, commencing near the 
western corner of Hereford Township, crosses the narrow part of District Township, and then the 
whole of Pike, following the eastern side of the Manatawny nearly as far down as the line 
dividing Amity and Earl. 

Mention has already been made of another tract of sandstone in the form of a ridge or spur, 
commencing about a mile E. of Spang's Furnace, and running in a N.E. direction into the 
region occupied by the gneiss. At Hill's Inn the limestone is found on the E. side of the 
Manatawny, dipping to the N.W. The sandstone immediately E. of this dips steeply in the 
same direction. A little N. of the Amity Township line, the sandstone, on the other hand, 
crosses to the west side of the creek. At the bridge on the Township Road, over the Manatawny 
Creek, the limestone, in its upper beds, is striped by reddish ribbons. A calcareous slaty sand- 
stone here occurs, precisely similar in appearance to the red sandstone of the Middle Secondary 
or Mesozoic rocks, of which it may be a detached or outlying patch. About a quarter of a mile 
below this, on the creek, is the general margin of the Middle Secondary red shale and calcareous 
conglomerate. 

The southern half of Earl Township includes chiefly long hills of syenite and other crystalline 
rocks, running in a N.N.E. and S.S.W. direction, having coarse Primal sandstone flanking them 
on their north-west slopes. Taking the road from Kline's Tavern, near the Manatawny, eastward 
to Boyerstown, the sandstone of one of these spurs, approaching from the N.E., shows itself 
on the road dipping 35° S.S.E. At the intersection of the road and the township line of Earl and 
Douglas, we enter on the margin of a small tract of limestone, overlapped further S. by the 
red sandstone. It crosses to the N. of this road. The limestone peeps out at a house laid 
down on the county map as Keely's Tavern, and shows itself again in a quarry a few hundred 
yards E. of the tavern kept by Mr Gresh. Near Keely's Old Stand the sandstone occm-s on the 
N. side of the road, and it again appears N.W. of Gresh's. The limestone to the S. of this 



HILLS EAST OF EEADING. 



201 



is overlapped by the Middle Secondary rocks. East of the limestone, and before reaching Ehoads's' 
Mill, we come, in succession, upon white gneiss, syenite, sandstone, and limestone, the latter 
appearing at the mill. From this point eastward to Boyerstown, the whole space is occupied by 
crystalline rocks, covered on their Southern margin by the Middle Secondary. 

All that part of Colebrookdale Township lying to the N.W., N., and N.E. of Boyerstown 
consists exclusively of gneiss. This forms innumerable hills, covered by a deep and rather fertile 
soil, the whole district presenting, in a succession of undulating outlines, a highly pleasing series 
of landscapes. The limit of the gneiss and overlapping Middle Secondary sandstone, passing 
through this township, from Rhoads's to the West Branch of Perkiomen Creek, I have already 
defined. 

A locality of crystalline limestone occurs in the centre of Colebrookdale Township, on the North- 
east side of a road. The spot is about three-fourths of a mile N.W. of the edge of the Middle 
Secondary red sandstone. Between this place and Swamp Creek lie several high hills, covered 
entirely with diluvium and fragments of sandstone. Hills of this description are common along 
the line separating the Middle Secondary region from the gneiss of the South Mountains. 
At Swamp Creek we enter a valley bounded on the N.W. by rounded knolls of the gneiss, and 
on the S.E. by the Mesozoic red sandstone. This valley contains several exposures of limestone. 
The first of these is on the West side of the stream, and belono;s to Peter Motha. A little N.E. is 
the quarry of Jacob Oberholz, and beyond this, in the same direction, the limestone occurs on 
the premises of Henry Staufier. At the first place the strata dip N.E. ; at the second, 
nearly S. 

A narrow belt of the Primal white sandstone commences just E. of the West Branch of 
Perkiomen Creek, and runs to the N.N.E., through Hereford Township, to the line of Lehigh 
County. It is bounded on the S.E. by the overlapping red sandstone, and on the N.W. by the 
gneiss. The white sandstone shows itself on the main road, passing through the centre of the 
township ; the rock dips towards the S. It is again well exposed on the East side of the 
main Perkiomen Creek, where the Sumneytown road crosses. 

We find a small insulated patch of the white sandstone in District Township, about a mile 
and a quarter N.W. of Hoof's Inn, where it occurs surrounded by an elevated table-land of gneiss 
rocks ; the sandstone is of a coarse texture. Passing from Hoof's Inn south-westward along the 
West Branch of the Perkiomen, we meet another spot where the sandstone undoubtedly exists in 
place ; this is about half a mile from the inn, on the S.E. side of the road. A little W. of this 
commences on the stream a narrow valley, extending down to John Rush's forge, where the 
mountains approaching close it in. The Old Mount Pleasant forges are situated near the lower 
end of this vaUey. Limestone shows itself a short distance above Rush's MiU (Hunter's on the old 
State Map), dipping S.S.W. It is again exposed in two fine quarries, one on each side of the creek, 
at David SchaU's forge (Thompson's on the old Map). In the more western of these quarries the 
limestone considered the best is of a dark-blue colour. According to our analysis, the rock in 
both localities is highly magnesian, the composition being in other respects also precisely similar ; 
the lighter-coloured variety containing, if anything, rather less foreign matter. The dip in both 
quarries is to the N.W. 

Iron Ores of the Primal Strata. — Before closing this description of the Primal rocks of the State, it is expedient 
to mention that large deposits of brown htematitic iron-ore are not unfrequent in the soil and detrital matter -which 
VOL. I. 2 C 



202 



SOUTH MOUNTAINS. 



rest upou the Primal newer slates. This is the geological position of the great mine on Chestnut Hill, four miles east 
of Columbia, the ore occurring in a sort of basin of the disintegrated slate. Throughout the Appalachian Chain much 
valuable iron-ore is discovered in connection with the same formation. The localities of these Primal ores of iron vrill 
be discussed in the general Chapter upon the Iron Ores. 



OUTLYING BELT OF PRIMAL ROCKS OF MILLBOUGH HILL. 



There is an insulated belt of the Primal strata skirting the Northern side of the solitary oval 
tract of gneissic rocks W. of Reading and S. of Womelsdorf, which appears to extend from a 
point nearly S. of Sinking Spring westward, a little N. to the county line of Berks and Lebanon, 
thence south-westward, terminating in the western spurs of Millbough Hill, N.E. of Shefferstown. 
It is narrow when intersected by Cacoosing Creek, but broad near its western termination, from 
the presence of two or three anticlinal flexures. The strata consist of both the Primal slates and 
Primal white sandstone, fragments of which rocks are strewn abundantly in many places along 
the base of the ridge, hiding the southern edge of the limestone of the Great Valley. 



CHAPTER V. 



SOUTH MOUNTAINS, SOUTH-WEST OF THE SUSQUEHANNA. 

The irregular chain of hills west of the Susquehanna River in Adams, Cumberland, and Franklin 
counties, called the South Mountains, is a broad zone of low ridges, consisting almost exclu- 
sively of the Primal strata. It is the North-eastern termination of the first continuous mountain- 
range of the southern Atlantic States, called in Maryland and Virginia the " Blue Ridge." 
Tracing it South-westward, this tract originates near Dillstown in a narrow point, expands 
rapidly towards the head-waters of the Conecocheague, beyond which it grows narrower again, 
and curves swiftly Southward. It has the Cumberland Limestone Valley for its Northern and 
Western boundary, and the red sandstone plain of Adams County for its South-eastern ; Green 
Ridge and Jack's Mountain on the Western border of Adams County are eminences in this 
hilly belt. 

In its geological constitution this tract is without much variety, for it contains scarcely any 
rocks except those of the Primal series. It is doubtful if the true Gneissic rocks anywhere 
reach the surface within its borders, and only in one or two localities have even the lowest 
members of the Auroral limestone been met with covering the upper Primal slates. Even of 
intrusive igneous rocks it embraces a singularly small amount, those met with being chiefly 
gTeenstone and trap-rock. 

The geological structure, or mode of stratification of this belt, is equally simple. The whole 
tract consists of two or three groups of high, narrow, nearly parallel anticlinal ridges, expanding 
and subdividing toward the S.W. These are composed of the Primal white sandstone. Between 
them are high parallel valleys and plateaus of the Primal upper slates, which, from being softer 
and more fissile, have been worn and trenched by the ploughing force of waters to somewhat 
lower levels than the more resisting, better cemented sandstones. The crests of the ridges are 
therefore stony and rugged, their flanks usually smoother, being formed chiefly of the slate. 

To trace somewhat more in detail the several leading subdivisions of the belt, the first, or 
most eastern, is an anticlinal ridge, the rising of which N. of Dillsburgh, forms the very com- 
mencement of the chain. Commencing there, close to the Yellow Breeches Creek, which for 
many miles flows near its Northern base, it rises and expands until nearly opposite SLippens- 
burg, where, already divided into two anticlinal prongs, it begins to subside, and finally sinks 
to the level of the Limestone Valley, about five miles E. of Chambersburg. A rather deep 
valley, that of Mountain Creek, follows this sandstone range on its South side, the whole distance 
out to the Cumberland Valley. It consists of the Primal upper slates, much intersected with slaty 
cleavage. At one locality, Pine Grove Furnace, there occurs in the middle of this range of slate 
a narrow band of limestone, marking the position of the synclinal axis, or keel of the trough, 
into which the formations have here been folded. 

To the S.E. of this slate valley of Mountain Creek there is a second long continuous range 
of the Primal sandstone, commencing to the S.W. of Dillstown, and running forward, with little 



204 



SOUTH MOUNTAINS, SOUTH-WEST OF THE SUSQUEHANNA. 



interruption, towards the State line, ending in a series of spurs N.E. and E. of Waynesburg. 
For some few miles from its point of origin, this hilly tract appears to include but one anticlinal 
flexure, and it probably continues of this simple structure to within three or four miles of the 
Gettysburg and Cliambersburg turnpike road ; but further S. it spreads, takes in a second, and 
then a third wave, subdividing into separate anticlinal ridges, until three of these branch off in 
succession, and die away in prongs projecting into the limestone of the Waynesburg VaUey. A 
fourth, called Green Ridge, runs more continuously forward, with one or two hitches in its 
course, until it is intersected by the State line. 

The North-eastern termination of the mountain, near Dillsburg, consists entirely of the lower 
sandstone, the altered slaty belt on the Southern side having disappeared between the Petersburg 
and Carlisle turnpike and the end of the mountain, in consequence of the subsiding of the axis 
of elevation. It ends in two principal ridges. In a rough valley between these occurs a yeUow 
porous sandstone, often indicative of iron ore, some of which w^as found on the surface near the 
end of the Southern ridge. A little N. of Dillsburg the limestone of the Cumberland Valley 
folds round the Eastern end of the mountain, and appears on Dogwood Run, S. of YeUow 
Breeches Creek, where it is covered by the overlapping rocks of the Middle Secondary series, 
consisting here of the calcareous pudding-stone, or Potomac marble, and altered red shale and 
red sandstone. 

Another section across the mountain, more to the S.W., extends from S. to N. along 
the Baltimore and Carlisle turnpike. The first important stratum of the hills is the usual grey 
silicious altered rock so common along their Southern side. North of this, about three miles 
from Petersburg, occurs the dark green slate, wdth its epidote and white intrusive quartz. 
Succeeding this is an extremely compact silicious altered slate ; and beyond this, a reddish grey 
rock, of the same series, containing specks of reddish felspar and small veins of epidote ; and 
near this the fissile talcose rock, several times mentioned before. North of these we pass a tract 
of low ground, and then a high rough ridge of sandstone, ascending w^hich we come to 
Mountain Creek, at Holly Furnace, not now in operation. Beyond this to the N. is another 
bold ridge, the northernmost of the chain, consisting also of the Primal white sandstone of the 
lower division, which here resembles closely the same rock as it occurs in Chiques Ridge, on the 
Susquehanna. The beds here have a steep southern dip of about 70°. This dip is e\ddently, 
however, an inverted one, as these are the loiver rocks of the formation, and He N. of a folded 
. anticlinal axis. Between the Northern base of this ridge and the margin of the limestone of the 
Cumberland Valley, a deep deposit of diluvial matter hides from our view nearly the whole of 
the slaty or upper division of the Primal rocks ; which, in consequence of its easy denudation, is 
commonly found in the valley at the foot of the mountain, thus covered by transported matter. 

Crossing the mountain by another section still further to the S.W., we find the following 
order of things. Beginning at Cumberland Furnace, and passing to the head-waters of Opossum 
Creek, the North-western ridges of the mountain, near Cumberland Furnace, consist entirely of 
the Primal white sandstone. In the ridge N. of Pine Grove the rock is a more talcose 
sandstone, belonging probably to a higher part of the formation. Large veins of white quartz 
are here abundant. A whitish talcose slate rests conformably upon the talcose sandstone, dipping 
with it to the S.E. This latter rock forms an admirable material for the in-walls of a furnace. 



SECTIONS OF THE STRATA. 



205 



and is used in that at Pine Grove. Immediately S. of Mountain Creek, near the furnace, 
occurs a thin interposed belt of limestone, used as a flux, and also taken across the mountain, 
into Adams County, for lime for the fields. This rock contains disseminated crystals of Fluor- 
spar. 

Associated with this limestone is a valuable deposit of iron ore, which has supplied the 
furnace here for a long time. It is of the kind usually found in our limestone soils, being 
technically the hrown hydrated peroxide, having a variety of structures. The analyses to be 
given will display the composition of one variety of the ore of this mine. 

The limestone is evidently one of the beds at the alternation of the Primal slate and Auroral 
limestone. Passins; the low ridge containinsi; the limestone, we encounter a bold mountain of a 
somew^hat talcose sandstone, two miles in breadth, containing probably an axis of elevation witli 
the rocks on its Northern side inverted. On the Southern flank of this ridge occurs a belt of 
altered silicious rock, including a narrow band of talcose slate ; and S. of this, a zone of 
green altered slates, charged with epidote and quartz ; and overlying this again, another belt, of 
a more silicious altered slate. It is interesting to observe the importance which a single belt 
of limestone will give to a locality. It has here given rise to a rich deposit of iron ore, rendering 
productive a most beautiful and sequestered spot in a chain of hills, elsewhere remarkable for 
their forbidding features and sterile soil. The calcareous rock is only developed to any extent 
near the furnace, though it is said to be visible at Dull's Saw Mill, three miles higher up 
Mountain Creek. 

A fourth traverse of the chain by the line of the Chambersburg and Gettysburg turnpike 
road, displays the following succession of outcrops and exposures of the rocks, and though these 
are not sufliciently connected to afibrd data for a structural section, they furnish some instruction 
as to the materials of which the tract is composed. 

Leaving the limestone near Fayetteville, and going Eastward across the belt, we meet for the 
first three miles only fragmentary matter, chiefly of the white Primal sandstone, fine-grained, 
and weathering flesh colour and yeUow, swept down from the hiU-sides. Approaching Steven's 
and Paxton's furnace the prevailing rock is a conglomerate, with pebbles of the size of a pea. 
The rock becomes finer -grained E. of the furnace, and assumes more the typical characters of 
the formation. Passing Grsefienburg Springs, a little E. of the furnace and the Toll-gate, we 
encounter the first clear exposure of Primal white sandstone, here in the condition of a bluish 
conglomerate with pebbles, ranging in size from that of a pea to that occasionally of a large nut. 
At this spot the strata dip 60° to S. 60° E. A little further on there is a second exposure, 
where the dip is more uncertain, but where the cleavage is distinctly 80° to N.W. ; the apparent 
dip is 35° to the same quarter ; the rock is a fine-grained sandstone. Fragments of the coarse 
bluish conglomerate are next met with, and still further on, in a shallow pit, one may see the 
Primal slates fuU of micaceous and talcose partings of a pale sea-green colour ; here the strata 
dip 85° to N. 30° W., and the cleavage planes 75° to S. 10° E. 

The summit of the ridge exhibits a dark-blue and greenish-blue indurated rock, weathering 
a dark brown, and evidently very ferruginous. It appears to be a band of the Primal slate in a 
highly metamorphic condition, approaching jasper. Its beds dip 45° to N. 70° W. ; its cleavage 
60° to N. 70° E. This rock is succeeded by Primal slates, under their more ordinaiy forms, and 



206 



SOUTH MOUNTAINS, SOUTH-WEST OF THE SUSQUEHANNA. 



the Primal white sandstone, much altered, and with a peculiar fracture ; here the cleavage dips 
20° to S. 20° E., the strata apparently dipping at a high angle westward. 

Approaching Willow Grove Tavern, we meet a more favourable display of the rocks. The 
white sandstone forming the face of a hiU a few hundred yards S. of the road, exhibits, as it 
sometimes does in Montgomery County, thin laminte, diifering in tint, and separated by sur- 
faces or films of well-crystallised mica. Here the dip is 70° to S. 80° E., the cleavage dipping 
in the opposite direction. From this point to Cashtown the strata display no outcrops deserving 
a record here. At Cashtown the rock is partially a conglomerate of a grey colour. Here we 
meet the margin of the unconformably overlying mesozoic red sandstone. 

The mountain-gap of the Gettysburg and Chambersburg turnpike divides the altered slaty 
rocks on the S. from the unaltered sandstone on the N., until in our progress Eastward we reach 
the summit, E. of which the altered rocks cross the road, to range North-eastward along the 
Southern ridges of the mountain. The sandstone ridges which constitute the North-western 
spurs of the mountain, near Caledonia Furnace, jutting towards Green Village and Shippensburg, 
ranging North-eastward, become the main body of the mountain, the altered rocks lying on the 
Southern side. The same bed of altered rocks which lies between Caledonia Furnace and Cold 
Spring, and which crosses the turnpike South-east of the summit, is seen on the Southern side of 
the mountain, crossing one of the head-waters of Conewango Creek. 

Crossing the mountain between Caledonia Furnace and Cold Spring, a distance of seven 
miles in a S.S.E. direction, no vestige of the white arenaceous sandstone is to be seen, until the 
foot of Green Ridge, at Cold Spring, is reached. The section displays rocks precisely similar to 
those on the East side of the mountain, on the railroad at Maria Furnace and at Holm's Creek, 
showing everywhere marks of alteration by igneous action. In the ridge W. of Caledonia 
Furnace occurs a talcose sandstone ; and a fourth of a mile S. of the furnace, a highly- 
altered jaspery slate. Half a mile S. of the furnace, we meet a grey, spotted, silicious rock, 
evidently an altered sandstone ; two miles S. of the furnace, a grey, altered, silicious rock, 
with dark blotches ; and two miles N. of Cold Spring, a greenish slate, spotted with epidote, 
and charged with much white quartz. One mile N. of the same place, a reddish slate, 
speckled with white, occurs; and half a mile nearer Cold Spring is a red, jaspery, altered rock ; all 
belonging, probably, to the thick system of slates composing the upper member of the Primal 
series, but greatly modified in texture by the intrusion of quartz, and by other igneous action. 
Throughout this section the strata dip invariably to the S.E. Though no anticlinal axis is 
visible, there is convincing evidence that the rocks have been upheaved along such an axis, and 
folded together, so as to make those on the N.W. dip in an inverted altitude to the S.E. — a 
feature very common throughout the -whole range. 



Fig. 25. — Section across the South Mountains along the Gettysburg R R. — 1 inch = 3 miles. 




A fifth section across the chain is furnished by the exposures of the strata along the Waynes- 



SECTION GETTYSBURG RAILROAD. 



207 



burg and Emmetsburg Turnpike, and the cuttings of the old Gettysburg Railroad. Leaving 
the Auroral limestone of the valley, and entering the hills, the first actual exhibition of the 
strata met with is a South-dipping mass of Primal upper slates supporting Primal sandstone. 
These are probably inverted, forming the North-western leg of a wide complicated anticlinal 
flexure, the South-eastern limb of which would seem to be in the ridge containing the tunnels, 
several miles to the S.E., where the Primal sandstone and Primal upper slate dip at a moderately 
low angle South-eastward. Within this anticlinal belt there would seem to be three other anti- 
clinal flexures, all lifting to the surface different portions of the Primal lower slates, and all 
showing a prevalence of moderately steep South-east dips, with rather steeper South-east-dipping 
cleavage. These lower Primal slates are highly indurated, and even decidedly crystalline, con- 
taining in some of their layers segregated specks, and even half-formed geodes of epidote, and 
other minerals. They bear strong general resemblance to the half-crystallised older Primal 
slates, just S. of Spring Mill. 

Passing now to the Eastward of the Green Ridge Axis, we cross a high slope of slate, 
apparently the upper Primal in a synclinal fold, and then traverse a succession of outcrops of 
the Primal white sandstones and slates, to the Eastern base of the high land called Jack's 
Mountain, at the foot of which the older rocks disappear under the mesozoic red sandstone of the 
plain of Adams County. 

The exposures in the sandstones near the Tunnel opposite Jack's Mountain, indicate a 
probable thickness of 1000 feet. Near the Tunnel at the North-west side of the mountain there 
is a hard epidotic rock, and not far from it highly -altered greenish slate, a rock found in several 
other locahties further W., and containing layers of grey slate spotted with epidote. Further 
W. occurs epidote with asbestos. 

Near Miney Run search was made many years ago for copper ore, but nothing was found 
to justify the expectation of finding a productive vein of that mineral. A small quantity of 
copper ore was once obtained, and a furnace built for smelting it, in a small ridge N. of Jack's 
Mountain, but the exploration was abandoned. The metal occurs in the form of a green and 
blue carbonate, with a little native copper. Evidently the ore is not abundant. 



DIVISION II. 



AUEORAL SERIES. 



In the South-eastern district, the principal Auroral strata are those of the magnesian lime- 
stone. The Auroral calcareous sandstone (Calciferous Sandstone of New York) is in a few locali- 
ties seen emerging from beneath it ; but this formation would appear not to have been continuously 
deposited in this region. The other rocks of the series, the Auroral argillaceous limestone (Tren- 
ton Limestone of New York), generally so rich in fossils, as weR as the overlying Matinal slates 
(the Hudson Kiver group of New York), have evidently been removed at an early period, before 
the deposition of the Mesozoic red sandstone, by wasting waters that spared only the Yery 
lowest formations of the Palaeozoic series. In some parts of the district the portion of the 
Auroral magnesian limestone which has escaped denudation is nevertheless of great thickness, 
not less probably than 2000 feet. It belongs, however, to the inferior part of the formation, 
everywhere comparatively destitute of organic remains, even in the more fossiliferous districts ; 
and to this fact, arising from some general cause, and to the prevailing scarcity of fossils in all 
the formations throughout the region S.E. of the Kittatinuy YaUey, we must impute their 
non-appearance in the belts about to be described. 

In the region before us there are three principal belts or tracts of the Auroral bmestone ; 
that of the Chester County Yalley, that of Lancaster and York, and that of the South Moun- 
tains, between the Delaware and Schuylkill. A fourth, but much smaller outcrop, appears in 
the midst of the generally overlying tract of the Mesozoic or Middle Secondary red sandstone, in 
Bucks County, near New Hope. I shall describe, in the order in which they are here mentioned, 
these several areas of the formation, all of which I consider to have been originally connected by 
portions since washed away. 



CHAPTER 1. 



GENERAL DESCEIPTION OF THE LIMESTONE VALLEY OF MONTGOMERY 

AND CHESTER. 

This interesting belt of the Auroral limestone, the borders of which have been already 
indicated in a previous Chapter devoted to the southern outcrops of the Primal sandstone, is 
worthy of a more full and connected description than it has yet received. Externally the tract, 
with its highly cultivated farms, numerous thriving villages, factories, furnaces, and mills full 
of prosperous industry, presents a scene unsurpassed in the United States. The soft, pictur- 
esque beauty of the plain or bed of the valley is much enhanced by the two ranges of slate 
hills, still clothed with the remnants of the natural forest. It lies between these like the deck of 
a slender shallow boat between its sloping sides. Its surface is in almost every part irrigated 
with running brooks of pure transparent water, and it is crossed by several swift-flowing, sparkling 
streams, as large as the rivers of some countries. The grandest of these is the Schuylkill. It is 
here a broad current, and bears deservedly the title of river. The enclosing hills, or two edges of 
the general upland, between which this valley lies, at an average depression of nearly 300 feet, 
are superbly carved into innumerable wooded ravines and narrow dells. This is especially true 
of the slope overlooking the vaUey on the South. From any point on the southern table-land near 
the head of one of its ravines, the view is truly enchanting : broad slopes of foliage and a shady 
dell fill the foreground of the picture ; wheat-fields and pastures, orchards and snug tidy farm- 
houses, many of them of the dignity of country mansions, occupy for miles the middle distance ; 
and the extended background is a rich succession of fading liiUs and far-stretching mountains. 
Breaking what might otherwise approach to monotony in the curves of the landscape, are here 
and there deeper gorges in the north and south barriers of the valley, furnishing waterway for 
the larger streams, the Schuylkill, the Wissahickon, the Brandy wine in both its Branches, 
and the Octorara. The narrower parts of some of these are precipitous, and so shut in and wild 
as to present a most grateful contrast, in their tangled foliage, rough rocks, and mossy clifis, 
w^ith the neighbouring scenes of open pastures and sunny corn-fields. 



NORTHEEN AND SOUTHERN BOUNDARIES OF THE LIMESTONE. 

This belt of limestone, which forms the Great Valley, and extends through the western half 
of Montgomery County, through Chester County, and Sadsbury and Bart townships, in Lan- 
caster County, commences about a mile and a half S.W. of WiUow Grove. Tracing it along 
its southern margin, we find it entering the northern corner of Cheltenham Township, crossing 
the Bethlehem Turnpike near the Punning Pump Tavern, a mile below Flowertown, and thence 
passing to Spring Mill on the Schuylkill, where it crosses the river and follows Gulf Creek, 
through Upper Merion Township, into Chester County. After passing the county. line, a little 
less than a mile S. of the Baptist Meeting-house, it foUows the foot of the South Valley Hill 

VOL. I. 2d 



210 



VALLEY OF MONTGOMERY AND CHESTER. 



al)Out the same distance N. of Glassley and N. of the Paoh, to within a couple of furlongs 
of the Warren Tavern, and from thence half a mile S. of the Steamboat Tavern, and some- 
what more to the N. of the Indian King. Near Downingtown the belt has decreased much 
in width, being little more than three-fourths of a mile broad. The belt passes about two 
furlongs S, of the town. From Downingtow^n, the foot of the hill indicates the margin of 
the limestone, which passes rather less than a quarter of a mile below Coatesville to Freeman's 
Mill, on Buck Run ; thence to Cloud's Mill, near Phillip's Tavern, on the Gap and Wilmington 
Turnpike ; and to the Octorara Creek, near the junction of Cloud's Run. In Lancaster County 
it follows Cooper's Run as far as the dam near the Valley Mills, but continues along the valley a 
furlong S. of the stream. We thence trace the same southern margin across the West Branch 
of the Octorara, about a fourth of a mile below Buckman's Tavern, and thence to Kuukle's and 
Eckman's Run, at which place the limestone terminates. On Eckman's Farm the line doubles 
back towards the E., and pursues nearly a straight course, by the Reform Meeting-house, to 
Buckman's Tavern ; thence running straight to the Octorara, a fourth of a mile above Noble's 
Factory. The greatest width of the limestone in Lancaster County is not much more than half 
a mile. Returning into Chester County, the northern boundary continues direct to Parkesburg. 
At Coatesville it passes one furlong and a half N. of the village. Two miles E. of Coatesville 
the belt widens, and the northern edge passes a fourth of a mile S. of East Cain Church. 
StiU expanding, the northern margin passes one-third of a mile N. of Downingtown to West 
Whiteland Township line, where it is within a furlong and a half of the Valley Turnpike ; and 
thence continues N.E. for about three and a half miles. The width of the hmestone, taken 
along the eastern township line of West Whiteland, is a little more than two miles ; and the 
northern margin is a nearly straight line from thence to the Valley Creek, which it crosses half 
a mile from its junction with the Schuylkill. As the belt passes into LTpper Meriou, it is over- 
laid on the N. by the red sandstone — a portion of which, jutting forward as far as the King 
of Prussia Tavern, conceals that part of the formation which lies to the N. of Reesville. From 
thence the northern line continues direct to within half a mile of Norristown, and, turning down 
towards Swede's Church, crosses the Schuylkill one mile below the bridge. Doubling S. a 
short distance from the river, it forms, in Plymouth Township, another loop, and then crosses the 
Ridge Turnpike at the fourteenth milestone from Philadelphia, and the Germantown Turnpike 
a little more than a quarter of a mile below the fifteenth milestone. It then passes into White- 
marsh Township, crossing the Wissahickon at Mather's Mill, a short distance below Sandy Run, 
following the run until it reaches the eastern extremity of the belt in Abington Township, near 
Willow Grove. 

Chemical Composition. — In its chemical composition this limestone is, with the exception of 
an occasional stratum, highly magnesian, and many layers contain the carbonate of magnesia in 
the full proportion (namely, about 45 per cent) requisite to constitute the rock the peculiar 
definite chemical combination called Dolomite. More usually, however, the amount of carbonate 
of magnesia is somewhere between 10 and 30 per cent. As a general rule, the lower part of the 
formation is the most magnesian. This portion contains likewise a larger share of silicious and 
talcose matter than the beds higher in the series. The lime which this limestone yields, though 
invariably more or less magnesian, produces, on the whole, a very superior cement, the magnesia 
present in it giving the mortar the property of concreting with more rapidity than belongs to a 



Picloi-ial SectioTi . along Left BiUlk of Srhnylkill . shevrin^ Matiaal LmiestoTW' fi-cmi Rpd SainLstone Mov HarrisUmn to Consholiocken Dam . 




T f I 1 o V is h r h t. r t 






TROUGH OF AURORAL LIMESTONE. 



211 



cement of lime aloue. Many of the more liiglily magnesian limestones can be made to furnish 
very excellent hydraulic cements. 

Geological Structure. — The general geological structure of this populous and rich limestone 
belt, though curious, is extremely simple. Measured from one extremity to the other, the lime- 
stone, coincident very nearly with the bed of the valley, has a total length of about 58 miles. 
Its eastern end is just N. of Abington in Montgomery County, and its western at the source 
of Big Beaver Creek in Lancaster. In form, it resembles very much a long slender fish ; and 
this likeness is increased when we include as part of it the two spurs into which the bounding 
narrow sandstone ranges of Edge Hill and Mount Washington terminate, near the Pennypack, 
E. of Willow Grove. As pictured in the Map, it resembles a slender gar-fish, fins and all, with 
its tapering jaws asunder. The widest portion of the valley is between the Wissahickon and 
Valley Creek, where, from the southern barrier of the Primal slate to the northern margin of over- 
lapping Ked sandstone, the maximum distance is nearly three miles, and the average distance 
about two and a half miles. From the East Branch of the Brandy wine it tapers very gradually 
and slenderly to its western termination. From the Wissahickon eastward it closes up much 
more rapidly, ending bluntly from the intrusion of the low anticlinal wave S. of Willow Grove, 
which spreads it into the broad snout already noticed. 

Trough-like Dip of the Limestone. — The general structure of this first main belt of the Auroral 
limestone is that of a long and slender basin or synclinal trough, the southern side of which is 
much more steep than the northern. From the neighbourhood of the Gulf Mills, a little west of 
the Schuylkill, to its western end, this oblique symmetry prevails with scarcely any interruption. 
The strata of the southern side of the valley dip perpendicularly, often a little overturned into a 
steep south dip, but sometimes inclined steeply in the normal direction, or northward ; and it is 
only towards the western extremity, where the whole trough grows shallow, and rises as it 
flattens up and thins away, that the north dip ceases to be steep. The strata of the north side 
of the valley, or from the synclinal axis northward, dip at an average inclination of about 45° 
southward, or more strictly S. 20° E. But even this inclination is not absolutely constant, for 
in the wider central division of the valley this northern part of the trough contains in some 
places one or two short, low, and narrow anticlinal waves. 

Between the Schuylkill and the eastern termination of the basin, the general simplicity of 
the synclinal structure is much more frequently interrupted by the presence of included anti- 
clinal flexures, the more prominent of which — ^s, for example, those of the Conshohocken Eidge, 
or Bethel Hill, Barren Hill, and that of the Church Eidge, with others already described — lift to 
the day conspicuous local outcrops of the Primal upper slate and white sandstone. This eastern 
end of the basin is obviously much more undulated than its central and western portions, and 
the greater frequency of compressed waves in the strata is evidently connected with that 
longitudinal prolongation of the still sharper folds which corrugate the narrow zone of Gneiss 
embraced between the Attleborough sandstone range and the southern edge of the red shale. It is 
indeed but a local exemplification of a very general fact, that of the westward declension and 
cessation of the stronger crust-plications entering Pennsylvania from New Jersey. The position 
of this great synclinal trough between two sets of flexures, one set entering and enclosing it from 
the N.E., the other from the S.W., proves its relation to the same general cause which has 
preserved the troughs of coal, converting them to anthracite in a part of the Appalachian Chain 



212 



VALLEY OF MONTGOMERY AND CHESTER. 



just opposite. Indeed the whole tract of the Atlantic Slope and the Appalachians, embraced 
between the Delaware and Lehigh on the N.E., and the Susquehanna on the W., is a tract of 
general depression of the crust lying between the two more uplifted districts, — that of the 
mountains of New Jersey and New York on the one hand, and that of the Blue Ridge and 
the Juniata on the other. If, while inspecting the geological map of the State to assist our 
conceptions, we lift away in imagination the superficial deposit of Mesozoic red shale and 
sandstone concealing a part of the older rocks of the Atlantic Slope, we shall perceive this 
sinking and dying-out of the north-eastern and south-western groups of anticlinals much more 
obviously. It is to this fortunate abatement in amount of vertical uphft of the crust in the 
district between the Delaware and the Susquehanna, that Pennsylvania is indebted for the 
inestimable advantage above her sister States to the N.E. and S.W., of so remarkable an 
extension southward, or towards the tide, of her fertile and iron-yielding Auroral hmestone ; and 
it is to the same cause that she owes her inexhaustible basins of anthracite nearer to the sea- 
board markets by very many miles than any of the other Appalachian Coal-fields. 



CONDITIONS OF METAMOEPHISM OF THE LIIVIESTONE. 

Throughout this limestone basin, the southern steeply upturned outcrop exhibits a far higher 
degree of metamorphism by heat than the northern, and this alteration appears greater where 
the strata approach most nearly the vertical position, and is greater still where they are inverted, 
that is to say, between the Wissahickon and the Brandywine. It is chiefly within these Hmits 
that the elsewhere bluish and yellowish limestone is in a condition of crystalline and granular 
marble, white, shaded, or mottled, from the dispersing and segregating action of a high 
temperature upon its changeable ingredients. An examination of the Map and Sections will 
show that all the marble quarries hitherto opened are included within this steeply upturned or 
overturned outcrop, the best of them lying within half a mile of the southern edge of the 
formation, or of some sharp inverted anticlinal like that of the Conshohocken Eidge. It is 
Hkewise along this most convulsed and cleavage-intersected side of the trough that, from the 
same cause, as will hereafter be explained, nearly all the largest, deepest, and richest deposits of 
brown iron-ore or haematite have hitherto been met with. 

Throughout the northern half of the basin, especially where the limestone observes its usually 
very regular southward dip of seldom more than ^5°, the rock is in the condition of a sub-cr}"stalline, 
and even earthy or purely sedimentary magnesian limestone, and its bedding is for the most part 
very uniform and rather thick. Its colour is a pale greyish blue, except in neighbom-hoods like that 
on the Schuylkill below Norristown, where a partial metamorphism has approached the northern 
border, and it is then, very frequently, a pale straw-yeUow and bluish white. The interleaved 
thin layers of argillaceous matter which so frequently separate the beds of the limestone are in 
the condition of an indurated clay-slate, but seldom show even incipient crystallisation. In 
many instances wide bands of the limestone, along its northern outcrop, exhibit numerous cross- 
joints intersecting the beds in nearly all directions, and causing the rock in certain quarries to 
break into a mere rubble of small angular fragments, assisting much the labours of the quarry- 
man and limeburner; but these joints, and the before-mentioned semi-crystalline texture, are the 



METAMORPHISM. QUARRIES. 



213 



limits to which the metamorphism of the rock has reached, a true parallel slaty cleavage being 
seldom or never discernible. 

But the state in which the very same beds exist, where they rise perpendicularly or with inver- 
sion to their southern outcrop after passing the synclinal turn in the centre of the basin, is very 
different from all this, and in striking contrast. The faintly crystalline and earthy limestone is 
here a distinctly crystallised, often a granular marble. Its colour is changed to a brilliant white, 
or to a mottling of purely white and dark blue, from the presence of segregated or half-developed 
graphite ; and the dispersed ferruginous matter is here in a state of minute solitary crystals of 
sulphurate of iron disseminated through the body of the stone. The rock, instead of lying in 
thick, often massive beds, is cleft into thin plates by innumerable natural fissures or cleavage- 
planes, not parallel with the stratification, but dipping steeply southward or acutely across it, 
and these fissures are filled and lined with distinctly crystalline flaky talcose and micaceous matter, 
sometimes talc and mica fully developed. The partings of slate between the limestone layers have 
been converted to laminae of talc-slate, in which there is often a cleavage-structure distinctly dis- 
cernible, much more intimate than that in the altered limestone, but dipping in j^arallelism with it. 
Viewed edgewise, a fresh exposure of the most altered limestone, such as is visible on the River 
Schuylkill near Conshohocken, has the aspect of a blue and mottled marble, streaked with films of 
talc, and shivered by innumerable cleavage-joints ; but viewed face- wise, the layers and fragments 
have the aspect of a talcose or micaceous slate, so copious is the covering of talc and mica upon 
their surfaces. (See Sketches of the Quarries.) 

QUAEEIES IN THE LIMESTONE, AND OTHEE PEACTICAL DETAILS. 

The portion of the formatiou which enters Abington Township is more slaty and fractured than that further to 
the W., and it also contains a larger amount of silicious or sandy matter. Those portions of the rock which are 
exposed, or are nearest to the sm-face, have in many places undergone partial decomposition, and have the appearance 
of a white calcareous sand. This sandy aspect of the limestone may be observed in all the quarries in the neighbour- 
hood of Sandy Eun, and also at many other localities. Unless the rock has undergone partial decomposition, the 
limestone is crystalline and granular. It varies in colour from blue to white, as a greater or less amount of carbonaceous 
matter chances to enter into its composition. Each of these colours is not confined to a particular stratum, but changes 
repeatedly in the same bed ; and, indeed, the area occupied by one particular colour is usually very small. 

The dip throughout the whole formation is remarkably uniform. Near Sandy Eun it is towards the S. and S.S.E. 
Quarries and pits have been opened on almost every farm along Sandy Eun. One of the largest in this vicinity is on 
the farm of Mr Fitzwater, near Fitzwatertown. The limestone is chiefly blue, the dip S.S.E., at an angle of about 60°. 

On the turnpike opposite Sellerstown, a limestone quarry of some size is wrought, the rock making an excellent 
lime. An extensive quarry of the same nearly white variety of the limestone exists on Mather "s farm. There the 
beds are crossed by very regular joints, giving the appearance of a stratification in another direction ; the true dip is 
towards the S. 

Near the Germantown Turnpike, about a fourth of a mile above the Plymouth Meeting-house, are good lime- 
stone quarries. Much of the stone in this neighbourhood is beautifully white, thougli some layers occur having a more 
or less bluish tint. The weathered surface of many beds is rough and sandy, showiug some silicious matter in the 
rock. 

Spring M^. — North of the Furnace 200 yards there is a large quarry in the limestone near the southern edge of 
the formation, in which the dip is 85° to S. 10° E. The southern side of the quarry is massive and jointed, and the 
dip planes are almost effaced ; the northern side is more thin-bedded and talcose, of a bluish-white colour, and its struc- 
ture very crystalline. 

In that portion of the Limestone Valley which occupies the southern part of Upper Meriou Township, especially 



VALLEY OF MONTGOMERY AND CHESTER. 



iu the immediate vicinity of the Schuylkill, there are numerous and extensive quarries, furnishing a large supply of 
the rock, a portion of which is transported to Philadelphia, and other places, by the several railroads and the Schuyl- 
kill navigation ; but a large amount is converted into lime on the spot, designed for the same markets. 

A large quarry of the limestone is wrought on the west side of the Schuylkill, two or three miles below Valley 
Forge, where the rock is tolerably thick-bedded, and of a light colour. The quarried stone is conveyed to the river by 
a railroad, and thence taken by boats to the various limekilns. Extensive quarries have also been opened near the 
Valley Church, where the limestone is very similar to that of the last locality, dipping steeply south, being of a light 
tint, and furnishing an excellent lime. On the road from Glassley to Valley Forge, near the county line, there is a 
small bed of slaty talcose calcareovis rock extending E. and W. about three furlongs in length towards Valley Creek. 
It constitutes a small hill, over the east end of which the road passes. Near Valley Forge occurs a stratum of 
felspathic rock like that seen at Barren Hill. It is exposed in the Creek, and occasionally appears overlying the 
Primal white sandstone at the foot of the North Valley Hill, a little East of the North Valley Church. The limestone 
near the White Horse Tavern in East Whiteland Township is occasionally talcose and slaty. Nearer the Steamboat 
Tavern the more usual gramdar structure prevails : throughout all this range, however, the rock yields an excellent 
lime. 

At Downington the limestone is chiefly of a light colour, and compact. Several quarries of compact and gi-anular 
limestone have been opened iu this vicinity. 

The width of the formation near the East Cain Church is reduced to about three-fourths of a mile. It is somewhat 
variable, being dependent, probably, upon the angle of the dip, which, however, is pretty constant. At Coatesville it 
does not exceed three furlongs. At Bell's Quarry, Midway, the rock is of a light colour. About one mile east of 
Trueman's Mill, we find a small bed of white day, derived from the decomposition of an altered felspathic slate, lying 
between the limestone and the talc slates. In the vicinity of Buck's Run and Parkesburg the limestone becomes 
darker and more slaty. Passing Cloud's Mills into Lancaster County, it gradually declines in thickness, being at 
Cooper's Fulling Mill, in Strasburg Township, not more than two furlongs wide. At its termination in Bart Town- 
ship it becomes more than usually sandy, especially near its margin. The main belt seems to terminate on Eckman's 
Run ; but another small lenticular belt shows itself a mile and a half further to the west, on the premises of Mrs 
Bare, where the rock is quarried. 

The practice of the landholders is to let out the right of working the quarry for a certain period, and the tenant 
during that time may excavate as much stone as he may require. Many quarries also are opened and worked by the 
proprietor for his individual supply. No record is therefore kept to enable us to ascertain the number of perches 
anuually quarried. 

TRAP-DYKES. 

Near the Meeting-house, about a mile above Flowertown, a trap-dyke crosses the Bethlehem 
turnpike in a N.E. and S.W. direction. It appears to contain labradorite. It is about two and a 
half miles long, commencing near the north-west line of Springfield Township, and ranging past 
Bickell's Mill, on the Wissahickon, to the School-house half a mile further W. The protrusion 
of the dyke has not disturbed the adjoining strata to any serious extent. A marble quarry has 
been opened S. of the dyke, near Beck's MiU. The rock is granular, and its predominant colour 
is bluish. Crystals of filiate of lime occur in this quarry. About half a furlong N. of the dyke 
there is another quarry on Bickell's Farm, in which the beds are somewhat contorted. 

Another dyke of trap crosses the Schuylkill near Conshohocken : commencing a little E. of 
the Perkiomen Turnpike, about half-way between Barren Hill and Marble Hall, it crosses the 
Norristown or Pddge Turnpike, ranges nearly along the crest of the Conshohocken ,Slate Eidge, 
goes through the village, and passing the river, in the bed of which it may be seen, it follows the 
summit of Bethel Hill into Delaware County, terminating near the road leading from the Lan- 
caster Turnpike to the King of Prussia Village. This is by flir the longest and widest trap-dyke 
of the valley or its borders, its length being a little more than six miles. 



MARBLE. 



215 



OF THE MARBLE OF THE LIMESTONE BASIN OF MONTGOMERY COUNTY. 

The quarrying of marble iu this district was commeuced about 75 years ago, by Daniel Ilitner. For the last 1.5 
or 16 years the average quantity sent from the quarries of Marble Hall, owned and wrought by the present proprietor, 
Daniel 0. Hitner, has been about 25,000 cubic feet. 

The belt of marble is nearly three-fourths of a mile wide. Marble Hall, on the Perkiomen Turnpike, is the east- 
ernmost point at which good building-marble is wrought, though the belt is known to continue further. It extends 
thence to the Schuylkill nearly to the Chester County line. 

The largest quarry of all is that of Marble Hall ; here the strata dip to S. 20°, E. about 85°, presenting in one or 
two places a flatter incliuation. This quariy is not less than some 400 feet in length, and at the top is 60 or 70 
feet wide. The greatest depth to which the quarry has been sunk is 2G5 feet. At this depth were procured the blocks 
of beautiful white marble sent by direction of the State of Pennsylvania, and by the City of Philadelphia, to the great 
monument at Washington. At this depth the stratum of white marble, for which this quarry is chiefly wrought, has 
a thickness of 5 feet ; but the usual thickness of this bed of pure white stone is 8 feet, that of the pure and clouded 
white together being generally about 20 feet. 

Mr Hitner has quarried blocks 6 feet in thickness, tliough the genei-al thickness of the blocks readily procurable 
does not exceed 2| feet. 

The only saccharoidal or statuary marble in this or any of the quarries, is found here at a depth of 120 feet, in a layer 
of only 6 inches in thickness. It is of a yellowish white colour and remarkable evenness of grain. 

The white marble is used for monuments, and for the finer architectural purposes. It now sells for about one 
dollar per cubic foot. 

To the south of the large quarry of Marble Hall, which, besides the white marble, yields much beautiful clouded or 
shaded stone, there is a quarry of blue aud black marble, distant about 300 yards. This is owned by Mr Lentz, but 
now wi'ought by Daniel 0. Hitner. This blue and black marble now sells for about 40 cents per cubic foot. It is 
used chiefly for fronts of buildings, for monument bases, »kc. The thickness of the good blue marble in this quarry 
is 22 feet, and that of the black variety 8 feet. 

Besides these quarries in the vicinity of Marble Hall, there are others about three-fourths of a mile north from 
Spring Mill ; one set owned by Robert T. Potts, another adjoining his by Mr Peter Fritz. The marble of Potts' Quarry 
is chiefly of the clouded variety, besides a little white and some plain blue. The annual yield of this quarry is about 
12,000 cubic feet. 

The quarry owned by Fritz is at present but little wrought. 

Next in. position to the westward, but still seated in the same belt, are two quai-ries westward of the Schuylkill ; 
these are Henderson's and Brook's, in Upper Merion Township. 

Henderson's, the ueai-est to the Schuylkill, aflbrds a plain blue marble, besides a little white. Both of these quar- 
ries are wrought at present to only a moderate extent. 

A little south of the Valley Turnpike, about three and a half miles E. of Downingtown, is the extensive quarry of 
superior white marble which has for many years supplied Philadelphia with the beautiful article employed iu so many 
of its public and private edifices. It is on the farm of Mr John R. Thomas. The beds on this quarry are slightly 
contorted. The portion worked for the marble separates into two bands. The rock occurs in massive beds, chiefly 
white, with sometimes a bluish tinge, aud is quarried with great facility. It has been much used in the construction 
of the Girard College and other public buildings which adorn Philadelphia aud the neighbouring towns. This marble 
is converted into a good lime, but its crystalline or granular structure causes it to crumble in the kiln, making it a 
little difiicult to manage. The lime from this variety is much esteemed by masons, being sold in Philadelphia under 
the name of Fish-egg Livu'. 

The blue-mottled limestone or marble of Whitemarsh, occurring at the quarries not more than three-fourths of a mile 
north of the northern limit of the Primal Strata, is evidently on the south side of the trough, or folded synclinal axis of 
the district. Th is is further proved by its great steepness of dip, about 80". It is, moreover, of the maximum degree 
of metamorphism or crystallisation ; contains talcose or micaceous laminse, and crystals of sulphuret of iron, <fec. 

Strontiq. — Near Mr Hitner's House, Marble Hall, there occurs a thin bed of very ponderous rock, resembling 
closely a white crystalline marble. It contains, however, but a moderate proportion of carbonate of lime, and consists 
chiefly of the carbonate of strontia. 



216 



VALLEY OF MONTGOMERY AND CHESTER 



LOCALITIES AND STATISTICS OF THE IRON-OEE BANKS OF THE LIMESTONE BASIN OF 

MONTGOMERY AND CHESTER COUNTIES. 

Uast of the SclmylJcUl. — The first ore ever dug in this valley E. of the Schuylkill was near Spring Mill, on the 
farm of J. Kirkuer, at the excavation near the road leading to Barren Hill. This was about 30 years ago. 

Hitners Banks, near Marble Hull. — Iron ore seems to abound in great quantity in the deeper trenches or basins 
upon the limestone or marble north of the Conshohocken axis. From one locality near Marble Hall, Mr Hitner drew, 
in 1852, about 10,000 tons of good ore, and in 1853 rather more than 12,000 tons. 

It is estimated by those best informed, that from the belt of country embracing the ore-pits at present wrought on 
this east side of the Schuylkill, the amount now taken is about 60,000 tons. This belt has a mean breadth of about 
one mile, extending from the Barren and Edge Hill range of Primal sandstone, northward to the middle of the valley 
beyond the narrower limit of the crystalline limestone or marble. Its length, as far as it has been hitherto explored by 
digging, is not less than seven miles. The ore is not equally plentiful all across this zone, but seems to range in long 
narrow strips, following, as it were, so many deeper troughs of ferruginous soil, covering the undulating outcrop of the 
limestone. The most productive belts seem to be one north of the Barren Hill range, and one north of the zone of 
white and clouded marble. 

Good iron-ore occurs in scattered localities north of the general margin of the broad belt here mentioned. Thus 
Mr Wood, about one mile north of Marble Hill, finds a shallow deposit of iron ore in soil overlying limestone. This 
limestone would seem to be very thin here, for sandstone is reached at a small depth below it. 

West of the Schuylkill. — There are several excavations for iron ore in the Narrow Limestone Yalley south of Bethel 
Hill. Two of these localities are east of the gorge by wliich Gulf Creek passes through that hill. 

One group of pits, or that which is nearest the Schuylkill, is somewhat more than one mile S.W. of it, and almost 
150 yards S. of the road along the north side of the valley. One of the pits is mined by Mr Whitehall, and the other 
by Mr Fisher. The ore, which appears to be excellent, is smelted at Merion Furnace. 

The old pit near the fork of the road, at the Baptist Meeting-house, has a shaft some 76 feet deep, and was soon to 
be reopened by the aid of a steam-engine. The ore is declared to be of superior quality. Formerly it partially supplied 
Merion Furnace. It is owned by Caldwell and Roberts. Tliis ore rests on white marble. Another old opening of ore, 
now neglected, lies almost 200 feet further east on the S.W. side of the road. 

About 100 yards N.E. of Henderson's Marble Quarry, in Upper Merion, is an ore-bank wTOught by George Fishei-. 
It is of considerable size, and until recently (1854) yielded good ore, but at present the brown hydi'ous oxide of iron 
has more earthy matter mingled with it than formerly. 

George Fisher has a second ore-bank about 1250 feet N.E. of the one just named : here the ore is tolerably good. 
A new opening connected with this supplies ore to the iron-work, at Phoenixville. In these banks the average pro- 
portion of dirt to ore is about three to one. 

Thomas Widdart's ore-bank, situated like those of Fisher on Henderson's property, is about 800 feet S. of 
Fisher's second opening. The quality of the ore here does not materially differ from that of the other banks. The old 
bank having nearly failed, a new one has been opened within the last two or three years. 

Milliton's Bank, on Jones' Land, is situated W.S.W. of Fisher's, near the School-house ; the ore is pronounced good. 
It is smelted at Jones' Furnace, above Conshohocken. In this excavation tiie proportion of dirt to ore is about three 
to one. 

Otto's Bank, on Potts' farm, contains good ore, but this has not yet been obtained in large quantities. Here the 
proportion of dirt to ore is about two to one. In 1854 this bank was but newly opened. Supplee and Hampton each 
have ore-banks in this vicinity, both of them of medium extent. 

Hughes and Jones have several ore-banks in one group, leased for mining by sundry persons. No one of these 
excavations is large, though they form a considerable group. 

The next neighbourhood in the valley at which iron ore is dug to any extent is in the vicinity of Howellville, Tredyf- 
fring Township. South of the village there is a small newly -opened ore-bank, from which good ore has been obtained. 

Another ore-bank, owned by Mr Wilson, lies N.W. of Howellville, on the Swede's Ford Road, and this was but a 
small digging in 1854. 

Woodman's ore-bank, on land of William Roberts, situated about 500 yards W. of the Yalley Forge Road, and 500 
yards N. of its forking with the Swede's Ford Road, yields an excellent ore. It contains the unusual proportion of 



LOCAL LIMESTONE BASINS. 



217 



two parts ore to one part dirt. The chief drawback is a rather copious influx of water. This ore is smelted at Phce- 
nisville. 

Nathaniel Jones and Charles Beaver have ore-mines near the Baptist Church, half a mile from Centreville. Buck 
and King have also opened a bank. All these three are in considerable excavations. 

Samuel Beaver has an ore-bank near the foot of the North Valley Hill, about half a mile S.E. of the head of 
Valley Forge Dam. This bank is of considerable size, and yields good ore. It is unusual to find so large a deposit so 
near the northern margin of the valley, though unquestionably the lower, more magnesian beds of the Auroral lime- 
stone are much the most ferruginous, and where they support a deep deposit of earth, largely derived from their own 
disintegration, they constitute one of the main sources of the surface brown iron -ores. 

Holland's Bank, about one and a half miles N.W. of Howellville, yields an excellent ore, which has been smelted 
at Phoenixville. The depth of the excavation, in 1854, was 43 feet. 

Still further West in the valley, or past the meridian of the Paoli, there occurs another district of successful ore- 
diggings : the first of these is William Buchanan's Ore-Bank, about 400 yards N. of Oakland Hotel, on the railroad, 
and 100 yards W. of a cross-road. This is an excellent deposit, portions of the bank yielding two parts ore to one part 
dirt. The ore is taken to Jones's Furnace on the Schuylkill. 

G. W. Jacob's Bank, situated between the North Valley and the Columbia Railroad, about two miles E. of Oak- 
land, is a comparatively new excavation, but a promising one. The same proprietor has two other banks, about one- 
fourth of a mile S. of the Ship Tavern, both yielding well. 

Maquire's Bank, on a cross-road, one mile N. of the Ship, is rather a large excavation of good ore. 

Mr Evans has an ore-bank three-fourths of a mile E. of the Ship, which yields ore of a superior quality, and gave 
indications, in 1854, of a large deposit. 

Frederick Neal's Ore-Banks, extending one-fourth of a mile upon a cross road, include three pits yielding good ore. 
He has a second opening ou Lea's estate, near the North Valley Railroad. When seen it was a small newly-opened 
digging, yielding a good ore. A mile or more N.W. of Downingtown thei'c is an ore-digging very near the foot of the 
North Valley Hill, but this has never been extensively opened, nor does it promise a large supply. 

West of Coatesville there have been two or three excavations for ore towards the southern side of the valley between 
the West Branch of the Brandywine and Buck Run, but these have never furnished large supplies. 

INSULATED LIMESTONE-BASINS IN THE PRIMAL ROCKS OF LANCASTER COUNTY, 
AND THEIR DEPOSITS OF IRON ORE. 

There are several small insulated basins of limestone in the district of Primal rocks between the Main S3rn- 
clinal Trough of the Chester and Lancaster Valley, and the Pecquea and Conestoga Valley. Eour of these lie 
in parallel arrangement to the North of the West end of the main Chester and Lancaster Limestone Valley, all 
of them crossing the Big Beaver Creek. They are separated by anticlinal undulations of the Primal strata, and 
are bordered by the upper Primal slates. Their positions are shown on the Geological Map. The two longest, 
the southern and the northern, exceed one mile and a half in length, for so far do the topography and the soil 
indicate the limestone to extend. The two central ones are shorter. 

Nearly "West one mile from the most northern of these four basins, but apparently with an anticlinal ridge 
between them, lies a fifth small trough, crossing a tributary of the Pecquea ; and North of this last is a sixth 
basin, the widest apparently of them all, intersected by the main stream of the Pecqiiea itself. It is on the 
margin of this little valley of limestone that Mylin's Ore- pit occurs. 



Fig. 26. — Section at Schenck's Ferry. — 1 inch= 500 feet. 




Between the Pecquea and the Susquehanna there lie three longer narrow troughs of the limestone, insulated 
by anticlinals of the Primal strata. The most southern of these lies in the Valley of Eshalman's Kun, termi- 
VOL, I, 2 E 



218 



IRON ORES. 



nating just at the river at Sclienck's ; this is about a mile and a half in length. It contains the Coleman Ore- 
Banks of the Safe Harbour Iron Works. 

Due North of this, about a mile and a half, there is a longer basin of the limestone, which commences 
within a mile of the Pecquea, and runs westward for about three miles, crossing the Conestoga at Safe Haibour, 
and terminating in a little cove in the hills, about half a mUe West of that point. This likewise contains iron 
ore; the margin of the limestone just West of the Conestoga, being the site of one of the deeper iron-ore pits of 
the Safe Harbour Company. 

Still to the North of the last-described valley of limestone, and distant from it not half a mile, approaching 
it indeed very closely at the Conestoga, is yet another long narrow basin, stretching for almost four miles 
from near the Pecquea, crossing the Conestoga just above Safe Harbour Iron Works, and heading up half a mile 
to the westward in a little valley in Turkey Hill, precisely like the preceding. This last and longest of these 
troughs of Auroral magnesian limestone promises to afford much iron ore. West of the Conestoga there 
appears to be a considerable abundance of this valuable mineral, in its usual position among the strata which 
just connect the limestone with the Primal slates, and this is the site of a mine of some extent and depth. 
Near the eastern end of the same limestone valley occur other, apparently more extensive, strata of the same 
species of iron ore, occupying precisely the same geological position among the passage-beds between the two 
formations. The ore-pits are called the Rathfon Ore-Banks of the Safe Harboui- Iron Works. 

In this as in most of the other mines of iron ore connected with the Magnesian limestone, the position of 
the ore is precisely at the junction of the limestone and slate ; it is indeed only a veiy ferruginous variety of 
the Metamorphosed Slate, regularly stratified and intercalated with it. 



Fig. 27. — Section of Rathfon Ore-Bank, Safe Harbour ; 
also Gantner Ore-Bank. 




Wherever, as is most generally tlie case, the strata are intersected with cleavage-planes, and these are not 
coincident with the bedding, the more superficial portions of the ore follow for a certain distance the cleavage- 
dip, running out and off, — setting back successively into other more open fissures, but collectively descending 
nearly perpendicularly with the generally vertical dip of the strata, as in the Rathfon Baidi. 



Fig. 28. — Section of Ore-Ground east side of Conestoga Creek, Safe Harbour. 




Pt. Mica, gneiis. Slntet 



Contorted bedding 
utid /oiiatiun purallel 
}vrp.J'aint 




Shaft depthyis ft. 

two level* 




A little to the West of the Gantner Ore-Dio-o-ino;s 
i> a. "° there is a jutting outcrop of a micaceous crystalline 
sandstone, probably the Primal white sandstone 
altered. It dips 45° to N. 1.5° W. North of this sandstone there is a band of ore at the South foot of the 
River HUl, or in a straight line about one-half of a mUe from the river. But the main range of the ore is just 
at the South foot of the tract of high ground occupied by the sandstone. The ore lies in decomposed sandy 



LOCAL LIMESTONE BASINS. 



219 



talco-micaceous slate between the sandstone, and an outcrop of limestone South of it. This important range of 
ore has been proved, and opened for a length of about half a mile. Its strike is N. 70°— 75°E. The accom- 
panying section exhibits the relations of the three ranges of ore of this vicinity to each other, and to the 
strata with which they are connected. 

Mylins Ore-Pit is an open excavation for ore at the junction of the limestone and black slates, in the little 
insulated limestone basin which crosses the Pecquea, at the mouth of the Big Beaver Creek. It is among 
the alternating beds which connect the two formations. This was a recently opened bank in 18.j4, and the 
product in ore that year did not exceed 3000 tons ; but the succeeding year it yielded about 100 tons per week. 
The ore itself is of only moderate richness. It is conveyed at present to Lancaster. 

The Conewango Ore -Bank occurs likewise at the junction of the Auroral limestone and the Talco-Micaceous 
slates of the Primal series. Magnesian limestone outcrops within 100 yards South of the Mine Shaft, which 
has a depth at present (1854)) of 54 feet. There is an open pit with an inclined plane for elevating the ore, the 
shaft and engine being used for pumping. The ore itself exhibits here a rather solid mass not very regularly 
bedded ; it is in fact the ferruginous slate disintegrated, and re-cemented by the action of the surface-waters, the 
whole mass consisting of more than one-third part of earthy matter. The ore itself has a richness of about 40 
per cent metallic iron, and it is said to produce a metal of excellent quality. It is smelted at the Conewango 
Furnace, and also at York Eurnace. The same year the product of the mine was 1 50 tons per week ; the 
bottom of the mass of ore had not been reached in the pits. 

A small insulated patch of the limestone has escaped denudation on the Little Beaver Creek, near the Fulling 
Mill, about two miles from Strasburg. No ore has been found in its vicinity. 



CHAPTER II. 

AURORAL LIMESTONE OF LANCASTER AND YORK COUNTIES. 

It is unnecessary to define in tliis place the very irregular boundary of this extensive tract 
of the Auroral limestone. Its Southern margin has been already traced in describing the Northern 
border of the Gueissic region, and its Northern limits will be given when we come to specify the 
outlines of the overlapping Red sandstone. Meanwhile an inspection of the Geological Map will 
convey a sufficiently exact idea of its shape and position. 

Except in a few localities, the strata of this belt exhibit a less degree of metamorphism than 
belongs to the great altered tract last described. Though evidently much acted on by heat, 
their transformation has not amounted to a crystallisation, and a change of its blue hue to the 
white or mottled tint. In some places, however, the igneous action has accomplished this, and 
imparted to the more argillaceous seams the composition and aspect of a talcose slate. 

It has been already mentioned, that this tract of limestone is traversed in an East and West 
direction, by a number of anticlinal axes. Many of these are closely-compressed folds of the 
strata, and such are not continuously traceable without great difficidty. The general Sections, 
from V. to VIII. inclusive, will sufiiciently explain its structure with the aid of the Map. In con- 
sequence of the inversion of the beds, forming the Northern side of each anticlinal flexure, the whole 
district shows a prevailing Southern or South-eastern dip, but at the same time, much inequality 
in the degree to which the rock is broken in different localities. In a district like that of the 
valleys of Lancaster and York, where the limestone is very extensively employed for building, 
and for conversion into lime for the soil, it is of the utmost practical importance, in seeking for a 
suitable site for quarries, to give close attention to the situation of the places in relation to the 
anticlinal flexures. It will be found to be almost invariably the fact, that the strata lying to 
the S.E. of each anticlinal axis, and possessing a rather moderate inclination towards that 
quarter, are more free from irregular joints, and less crushed and shattered, than those upon the 
turn of the axis, or belonging to the inverted or northern side. Where sound rock is desired, 
the first position should be sought, and where broken stone is wanted, the latter. 

In its chemical composition, there is no difference between the rock of this tract and that of 
the Chester County Valley. Investigations in the laboratory have shown it to contain quite as 
much magnesia in the corresponding parts of the formation. Many of the inferior layers, those, 
for example, which are exposed on the Lancaster and Harrisburg Railroad, upon the prolongation 
of the anticlinal of Chiques Ridge, are so magnesian as to be regarded as almost a true 
Dolomite. 

The lower portions of the Auroral magnesian limestone are perhaps nowhere in this district 
better exposed than on the Susquehanna River below Columbia, near Strickler's Run, where they 
are seen passing, by a gentle gradation, with alternations, into the upper strata of the Primal 
series. An anticlinal in the ridge N. of Charlestown lifts the Primal sandstone to the level of 
the river, and from this point for half a mile N. to Strickler's Run, the Primal newer slate is 
exposed with a steep inverted and somewhat contorted dip, and an excessive amount of cleavage. 



TRAP DYKES. 221 

At Strickler's Run we meet with the lowest members of the Auroral limestones. Commencing 
with it, and proceeding northward, the strata are as follows, in the ascending order : — 

1. Limestone, apparently very magnesian, sub-crystalline, of a light blue colour, with white spots and streaks. Dip 
nearly vertical and parallel ; thickness, 150 feet. 

2. Blue talcoid slate, about 200 feet thick. 

3. Limestone, mottled blue and white, and coarsely crystalline ; thickness, 15 feet. 

4. Dark blue slate ; 20 feet. 

5. Limestone, crystallised and brecciated ; the fragments flat, white, and coarsely crystalline, cemented by blue 
and less crystalline limestone. The occurrence of altered fragmentary limestone so low in the formation is not a little 
ciu"ious. 

6. Bluish talcoid slate, 200 feet. 

7. Limestone, crystalline magnesia, blue with whitish blotches. Dip nearly vertical, rather towards the South. It 
is intersected by irregidar cleavage- planes, dipping generally 75° S. This outcrop is at the head of the sluice-way of 
the Columbia Dam. 

On the Northern side of the synclinal trough contained between the anticlinal below 
Strickler's Run and that of Chiques Ridge, some of the same beds reappear. 

The lower members of the limestone, those in alternation with the higher Primal slates just 
above Columbia, have been already treated of. These lower beds are seen in the corresponding 
part of the formation opposite the ends of Welsh Mountain and of Chiques Ridge. In relation 
to the cleavage, so conspicuous in the strata in this vicinity, a marked difference is observable 
between its dip on the two sides of the synclinal basin of Columbia, that of the steeply-dipping 
inverted rocks of the Southern anticlinal having, as we have seen, an inclination of 75° S., and 
that of the more gently-dipping beds of the Southern side of the Chiques anticlinal, a steepness 
of only 45° S. This is one instance among many proving that the original planes of deposition 
have exerted some degree of control over the subsequently-formed cleavage-fissures, tending to 
approximate them to parallelism with themselves. 

The most Eastern appearance of the limestone in the large tract before us, is in the narrow 
valley of the Eastern Branch of Conestoga Creek, at a point three miles E. of Morgantown. 
Here the formation emerges from beneath the Mesozoic red sandstone, at the foot of the Welsli 
Mountain. The limestone along this valley has a general dip to the N.N.W. It varies in colour 
from blue to white and pink, and in some places is much mottled. These deviations from the 
ordinary blue tint, indicate more or less igneous actions, and a greater or less proportion of 
magnesia and other extraneous ingredients. Some of the striped and mottled layers would yield 
a marble of a pleasing aspect, susceptible of a moderately good polish ; but the difiiculty is 
to discover among the north-dip^Ding strata, an outcrop of beds sound enough to be quarried 
successfully, so generally is the rock, in this position, seriously shattered and jointed. 

Trap Dykes, <&c. — Near Morgantown, the strata are contorted. Layers of chert are here 
met with, embedded in the limestone. In this valley there are three dykes of trap-rock, all 
observing nearly a N.N.E. and S.S.W. direction. 1st, The first of these occurs a little E. of 
Churchtown. It has not perceptibly affected the texture of the limestone with which it is in 
contact. 2d, The second originates at the Conestoga Creek near Penuytown, and extends for 
more than one mile in a S.S.W. direction. 3d, The third crosses the Waynesburg and Lancaster 
Turnpike, about half a mile above the Sorrel Horse Tavern. Approaching New Holland, the 



222 AURORAL LIMESTONE, YORK COUNTY. 

limestone becomes silicious, and is much intersected by veins of igneous quartz, the fragments 
of Avhich strew the surface. 

About a mile N. of the end of the anticlinal of Welsh Mountain, there is a belt along 
which the strata are nearly horizontal, marking the centre of the basin N. of that ridge. The 
city of Lancaster is situated upon a tract of deep blue limestone, containing thin seams of talcose 
slate, all dipping 60° S. This belt is the prolongation of the south-dipping zone of the Southern 
side of the anticlinal of Chiques Eidge. The rock contains much sulphuret of iron in cubical 
crystals, the decomposition of which has imparted to the soil in many places a dark brown 
ferruginous hue, and has been the obvious source of the iron ore disseminated in numerous small 
deposits throughout the neighbourhood. 

Near Millerstown, and also about three miles W. of Lancaster, there are several small dykes 
of trap-rock, which appear to have influenced, though very locally, the dip of the limestone in 
contact with them. Around Litiz the prevalent dip is towards the S. and S.S.E. Near 
Euphrata a quarry was opened a number of years ago, from which were obtained some good 
pieces of marhle of a very light blue tint, and some of it decidedly shaded. A considerable 
quantity of chert occurs at this locality. 

Auroral Limestone in the Valley of Yorh. — Passing to the Western side of the Susquehanna, 
we observe that the belt of limestone is there much contracted in its width. Its Southern 
margin is near Creitz's Creek, below Wrightsville. Here it is quarried on the South side of the 
creek ; another large quarry occurs on the North side of the same stream ; while a third, in which 
we find some beds of variegated limestone, is wrought a little N. of the bridge. The Northern- 
most exposure of the rock near the river, is in a quarry a quarter of a mile above the bridge. 
The limestone here is nearly white, and has the aspect and texture of a marble, but is much 
traversed by cross joints, and is hence difficult to procure in large blocks. From this vicinity 
towards York, we notice several varieties of the limestone, some belts of which are highly 
magnesian. 

The town of York is scarcely a mile from the Southern border of the limestone ; and the 
excavation for the railroad, a little S. of the town, shows it to be slaty, denoting its passage 
into the slate on the S. North of the Codorus it is extensively quarried and converted into 
lime. One mile N.W. of the town are extensive quarries, in one of which occurs a beautiful 
flesh-coloured marble, but not in beds thick enough to be profitably wrought. On a hill half a 
mile W. of the town, a variegated, silicious, and calcareous rock is quarried for a bmldiug-stone. 

That part of the limestone belt S. of the Pigeon Hills ranges between their Eastern end 
and the slate ridge to the S., and passing by Spring Forge, advances towards Hanover. 
S.W. of the forge, the belt becomes quite narrow and interrupted by bands of slate ; but it may 
be traced continuously between the Slate Eidge, or " Barren Hills," on the S., and Pigeon 
Hills on the N. 

Iron Ore. — A belt of iron ore is traceable along the Southern edge of this limestone, near the 
slate, for several miles. It passes a little S. of Hanover, and thence towards Littlestown. 
This ore was mined many years ago, but lay long neglected, owing to the inferior quality of the 
iron which it produced when smelted with charcoal, in consequence, chiefly, of its containing a 
considerable portion of the oxide of manganese. It occm-s in quantity in a small hill two miles 
S.W. of Hanover, and at many other localities, and of late years has been successfully mined 
on a large scale. 



LIMESTONE, ADAMS COUNTY. 



223 



The red sandstone passing from the "West end of the Pigeon Hills, encroaches upon the lime- 
stone as it advances S., until, near Arnold's Mill, at the State line, it overlaps the whole of the 
formation. 

Along the Southern base of the Pigeon Hills, in the slates N. of the margin of the narrow 
zone of limestone abeady traced, we find another belt of iron ore, of less length than that on the 
South side of the limestone. At Mold's, five miles N.E. from Hanover, the ore was dug about 
forty years ago. Much of it is scattered about the fields. Huge rocky concretions of ore pro- 
trude themselves at the base of a spur of the Pigeon Hills, about three-fourths of a mile to the 
N.E. The thickness of this deposit of ore is very great, not less perhaps than 100 feet ; but the 
mineral is extremely silicious. 

Limestone. — The Northern border of this division of the limestone, after ranging along the 
Southern side of the Pigeon Hills, folds round their South-western termination, and meets the 
overlying red sandstone on their Northern declivity. Extensive limestone quarries, producing a 
valuable lime, occur near the end of the hills. A limestone quarry exists on a farm near Cone- 
wango Chapel. Some of the beds yield a fine, compact, light-coloured variety, promising to be 
susceptible of a good polish as a marble. It affords a good lime. 

The Northern division of the limestone is overlapped, as we have said, along the Northern 
base of the Pigeon Hills. It appears, however, a little E. of King's Tavern, ten miles from 
York. The course of the Southern margin of the overlapping red sandstone from this point 
is nearly N.E., passing within two and a half miles N.W. of York. Between York and the spot 
at which the limestone disappears at the base of the hills, it is much traversed by small ranges of 
slate. 

The anticlinal ridge, consisting of the white Primal sandstone and slate prolonged from 
Chiques Eidge at the river, ranges along the Northern edge from Wrightsville nearly to York, 
within a mile and a half of which it terminates. The limestone folds round its Western end, and 
extends North-eastward between this ridge and another of silicious slate, running Westward from 
the Codoms. These uniting, the limestone ends in a point N. of the belt of silicious slate 
just mentioned, which belongs, apparently, to the upper portion of the Primal slate. We find 
another small wedge-shaped tract of the limestone crossing the river below Bainbridge, and 
extending Westward about a mile, when it is overlapped by the red "Sandstone, about a mile 
N. of New Holland. About half a mile W. of the river, near its Southern margin, we find lumps 
of iron ore in the soil. 

Auroral Limestone at the Southern Base of the South Mountain in Adams County. — There is 
a narrow outcrop of the limestone near the foot of the South Mountain in Adams County, which, 
being of some economical importance to the agricultui'e of the neighbourhood, merits a brief 
description in this place. 

The most North-easterly point at which we observe it is about a mile and a half north of 
Petersburg, where a beautiful white and compact variety is opened in a quarry. About half a 
mile S. of this, on the opposite side of a trap-ridge which intersects the formation, are other 
quarries. The rock is here of a light grey colour and remarkably soft, having been further 
removed from the influence of the once heated trap-rock. Another extensive quarry occurs in 
the same neighbourhood, two miles N.W. from Petersburg. Much search has been unavail- 
ingly made for limestone among the hiUs near the base of the mountain, ten or twelve miles 
Westward of Petersburg. The lime at present used is all brought from this latter place. 



224 



INSULATED TRACTS OF LIMESTONE. 



The next point at which we notice the limestone is about two miles N. of Fairfield. The 
rock here is of several shades of colour — purplish, greenish, and some of it nearly white ; it is also 
crystalline. On the West side of the Middle Creek, below Myers' Mill, it again shows itself, but 
is not quarried. The paucity of the exposures of limestone through this belt of country is due, 
unquestionably, to the extensive manner in which the older rocks are overspread by the Middle 
Secondary red shales and sandstones overlapping everything as far as the base of the hills. 

SMALL INSULATED BELTS AND QUAKRIES OF LIMESTONE SOUTH OF THE 
MIDDLE SECONDAEY RED SANDSTONE. 

In the district S. of the Middle Secondary red sandstone, there occur scattered, especially through Chester 
and Lancaster, a multitude of small patches — closely-folded basins I conceive them to be — of the Auroral 
limestone, bordered in some instances, though not in all, by the Primal white sandstone. S. of the Chester 
County Valley they lie almost invariably within tracts of the semi-metamorphic rocks, or crystalline Primal slates, 
but N. of that Auroral basin many of them are in the midst of what appears to be gneiss. 

Proceeding in our description of these from E. to W. as usual, it will be convenient, for the purposes of 
classification, to note and trace those first which belong to the districts S. of the syncHnal troughs of the 
Montgomery and Chester Valley and the Lancaster Valley, and then to review those that appertain to the 
Gneissic region of the Western part of Chester County. 

It will be seen, I think, that by far the greater number of these insulated outcrops and small basins of 
limestone, though probably not the whole of them, are, with whatever rocks they are in contact, only outlying 
patches of the great Auroral limestone of Southern Pennsylvania, folded, metamorphosed, disguised, and 
mineralised by intense igneous action, or that transforming agency which invaded all the older formations of the 
district in which they occur. Many of the lesser and more insulated of these outcrops of limestone show them- 
selves only in solitary quarries, but even in the great majority of such instances the topographical and geological 
structiire of the adjoining ground strongly imply the existence of smaller or larger basins, or true synclinal 
troughs, resting sometimes on the gneiss, but in most cases embraced as folds within the talcose micaceous 
slates, which, upon the view I have adopted of the metamorphism of our rocks, are only the upper and lower 
Primal slates of the base of the Palaeozoic system altered and crystallised. The limestone of these tracts 
exhibits all gradations of metamorphism, from the first change from earthy limestone to compact crystalline 
clouded marble, on to granular limestone and dolomite, and even to the most coarsely-crystallised calc-spar, with 
segregated crystalline graphite. In some cases the rock is almost pure carbonate of lime; in others, it is a 
true dolomite, or double carbonate of lime and magnesia. In some instances, again, it is free from any foreign 
minerals ; while in sundry other cases there abound numerous mineral species in all stages of segregation or 
development, from the most vaguely-formed crystalline nuclei to the most perfectly definite crystals. In 
certain examples we may distinctly trace the minerals through all these gradations of evolution, while in other 
instances we can ascribe their presence only to intrusive veins of true igneous or volcanic mattei-, bringing 
the foreign substances into the limestone, or commingling them with it. 

The most Eastern locality of crystalline limestone in the district of the State we are now studying, is that of 
C Vanartsdalen in Bucks County, about three miles W. of Attleborough. This should properly be enumerated 
among those in contact with the Gneissic rocks, for it is surrounded by hard crystalline hornblende gneiss. It 
stands aloof, at a distance of one mile, from the Edge Hill zone of Primal white sandstone which traverses Bucks 
County South of Attleborough. A hornblende gneiss is in contact "with the limestone both N. and S., and 
even splinters and small blocks of the dark gneiss are involved in the crystalline limestone, as if ruptured 
from the walls of a fissure, through which the carbonate of lime of the quarry and the included minerals may 
have gushed ujj. Some of the thinner of these flakes of gneiss are excessively contorted and folded, indicating 
the whole mass to have been at one time in a pasty state, and so heated and squeezed as to have softened and 



QUAERIES SOUTH OP CHESTEE VALLEY. 



225 



folded the included gneiss. The limestone itself is a white crystalline mass, consisting of true granular lime- 
stone, granular dolomite, and calc-spar, full of specks of perfectly and imperfectly crystallised pure graphite, and 
replete with a variety of other interesting minerals. Some of these extraneous minerals exist as solitary crystals 
invested by the limestone, but the chief part occur in bunches and irregular veins through the general calcareous 
mass. It would seem as if some of these bunches and vein-like included masses had been elaborated from 
the materials of the gneiss caught in and melted up with more or less of the elements of the limestone. 
We are naturally led to this inference when we find that we can trace a regular gradation from the percep- 
tibly stratified gneiss into these contorted strings and bunches of the crystalline minerals surrounded by or 
dispersed through the limestone. Some of these veins or strings of mineral matter present themselves in one 
part as true veins of felspar, modified at its edges by the presence of much crystallised mica and graphite. 
These felspar injections consist of tolerably pure labradorite. In some places the limestone includes large 
bunches of serpentine, associated with talc and other magnesian minerals. The presence of these naturally 
suggests a possible origin by segregation, either in full or in part, from the dolomitic layers of the originally 
magnesian limestone. The quarry also includes blotches and little nests of calc-spar and serpentine, and again 
of calc-spar and coccolite, sahlite, scapolite, and sphene. Mica occurs in several beautiful varieties, and graphite 
both in large regular hexagonal crystals and in curved irregular plates, and also in fibrous bunches. 

It is worthy of remark that neither brucite nor spinel seems to occur here, though some of the conditions and 
associations are such as to suggest at first a hope of finding them. 

The whole exposure of the limestone is between 200 and 300 feet long, and about 50 feet wide, and the 
quarry is opened on the South side of a small valley at the base of a low bordering hill. This valley may 
possibly be the remnant of a trough or basin of stratified magnesian limestone invaded by igneous injections 
along its Southern margin, and the fused and metamorphosed portions, as exposed in the quarry, may be almost 
the sole remnant of the mass reserved to us from a wasting denudation. 

LIMESTONE QUAEEIES OF CHESTER COUNTY SOUTH OF THE GREAT VALLEY. 

Belt First. — Giving our attention now to the limestone basins and quarries of Chester County S. of the 
Great Valley, we find that they nearly all lie to the W. of the Brandywine, and are so related as to constitute 
or to suggest the existence of at least 6 or 7 long and narrow limestone troughs or basins. 

Browns Quarry. — The most Southern of these within the State is a narrow trough ranging S.W. a 
length of more than two miles, from near the Delaware State line to near the forks of Whitely, or Whiteclay 
Creek. This narrow belt is bordered on both sides by gneiss, chiefly of the hornblende kind. Three i^rincipal 
quarries occur in the tract. The first encountered in going S.W. is Brown's Limestone Quarry, on a tributary 
of the East Branch of Wliitely, near the Delaware line. It contains but little of the pure white limestone, 
the rock being much metamorphosed, and rather fuU of mica. It is, however, regularly stratified, and the 
lime furnished is well adapted for agriculture. 

X). Nevinss Quarry. — This is situated to the S.W. of the preceding about three-fourths of a mile, being 
on the E. side of the East Branch of Whitely Creek. The strata dip at a gentle angle South-eastward, and 
a low anticlinal undulation or saddle lifts the talcose slates underlying the limestone to the level of the bed 
of the quarry, proving the total thickness of the limestone not to exceed 40 or 50 feet. This quarry likewise 
contains a small amount of white limestone, much brown mica occurring throughout the upper beds. It yields, 
however, a pretty good lime. The limestone is overlaid by the ordinary very micaceous rock, dipping on South 
side of quarry gently S., and there is a dyke of granite at the S. margin. 

J. Nevinss Quarry. — This is the furthest opening South-westward within this belt, and seems to be near its 
termination. It is between the two branches of Whitely Creek, one mile above their junction. It has been 
wrought for 30 years by Mr J. Nevins, and includes both the blue and white varieties of the crystalline lime- 
stone. The white variety is a coarsely crystallised dolomite, producing an excellent lime for building. This 
occurs in massive beds in the lower part of the quarry, through a thickness of 20 feet. Above it there lies, in 
VOL. I. 2 F 



226 



INSULATED TRACTS OF LIMESTONE. 



equally massive layers, a variety streaked with bluish and brownish bands, deriving its colours from the presence 
of an abundance of bronze-coloured mica. Tliis coloured rock produces a grey lime. An anticlinal axis or 

saddle runs longitudinally through the quarry in a direction about N. 60° E. 

Fig ^9 Ncvins's Oiitirrv 

On the North side of this saddle the dip is about 45°, under a micaceous gneissic- 



by which the Gneissic rock is brought to lean over or rest upon the limestone which it elsewhere supports. 

Fragments of altered white sandstone occur in the vicinity of the quarry, to intimate that this is reaUy a 
compressed trough of the Primal and first lowest beds of the Auroral strata. Tlie whole breadth of the valley 
embracing the trough of calcareous rocks is not more than 200 yards. 

There is a quarry of limestone in the State of Delaware, about three miles S. of the State line, distant 
about four miles from the above-described one of J. Nevins, in a direction not far from S. 30° E. 

Belt Second (or that of Kennet Square.) — A line of detached limestone quarries extends from a point one 
mile S.W. of Chadd's Ford, on the Brandywine, to the East Branch of 'Whiteclay Creek, near Avondale Post 
Office. A branch of this trough, apparently a narrow or compressed fold in the strata, commences at Nickle's 
Quarry, includes Mendenhall's, which is likewise in Pennsburg Township, and embraces Goss's Quarries near 
Redclay Creek. It passes or unites with the Southern side of the main Kennet Square Basin in the vicinity 
of Pierce's Paper Mill. In the quarry of Mr Mendenliall the limestone is scarcely at all exposed, for, as Mr 
Mendenhall alleges, it lies very deep. It is overlaid by sandstone, which exhibits an apparent dip of 35° to the 
S. on the South side of the Quarry. 

The main Kennet Square limestone-basin, divided from the foregoing narrow trough by a ridge of dark 
hornblende gTieiss, extends from a point nearly N. of Goss's Quarry, to the East Branch of Whiteclay Creek, 
near the Avondale Post Office, as above mentioned. This trough is itself divided at its Eastern end by a 
vsdde low anticlinal hill of the Primal white sandstone, upon which the village of Kennet Square is seated, 
separating it into two branches or subordinate shallow basins. These coalesce into one wide basin a little W. 
of Kennet Square at the West Branch of Redclay Creek. Here the valley has a width of more than three- 
fourths of a mile, but the limestone does not apparently everywhere underlie it. This rock is quarried at 
Hoopes's, near the Creek. From this neighbourhood the belt steadily contracts to its Western termination beyond 
the East Branch of Whiteclay. The trough is bounded on the S. by hornblende gneiss towards its Eastern end, 
and by the lower Primal slates in the condition of micaceous and talcose slate towards its Western. On its 
Northern side the Primal white sandstone, underlaid by highly-ciystalline Primal slate, everywhere borders the 
limestone at the foot of the Toughcanem Hill. The uncomformable relation of the Primal rocks and limestone 
to the gneiss is nowhere better shown than along the Southern side of this basin in the vicinity of Redclay 
Creek, and nowhere have we more convincing proof that the white sandstone and micaceous slates associated 
with it, bordering this trough, are of the true Primal series ; for here they not only dip beneath the limestone 
all along its Northern margin, but rise in a regular anticlinal saddle through the limestone to divide the basin 
into two regular troughs. Throughout this belt the limestone, wherever it is exposed, has a highly crystalline 
structure, and the greater part of it is more or less magnesian or dolomitic. The Branch Basin south of Kennet 
Square exhibits a deep deposit of sand in the bed of the valley, extensively concealing the limestone. As 
already stated, the village of Kennet Square itself rests on Primal white sandstone. 

Belt Third. — Next in order, proceeding Northward, is the longest and most continuous of all these limestone 
troughs. This commences on the E., near the Red Lion Inn, on the old street road, half a mile W. of the E. 
boundary of East Marlborough Townshij^, audit ranges, curving gently Southward a distance of about nine mUes, 
nearly to the Middle Branch of Whiteclay Creek ; the trough is broadest between the West Branch of Redclay 
Creek and the East Branch of Whiteclay Creek, having there an average breadth of more than half a mile. The 
Western half of the whole basin is subdivided into three subordinate narrower valleys, all of them containing 
the limestone, more or less continuously, and all of them ending Westward in the vicinity of West Grove 
Friends' Meeting-house. 




looking rock. The dip on the South side of the quarry is to the S. about 30°. 
A contortion along the Southern edge of the quarry, and in the gneiss-like 
rocks which border it, presents an unequivocal indication of an inversion or fold 



UPLIFTS OF GNEISS. 



227 



(1 .) The first or most southern branch leaves the main basin about midway between the West Branch 
of the Eedclay and East Branch of Whitechiy, and runs as a narrow, somewhat irregular trough for more than 
three miles, to a point a little E. of West Grove Friends' Meeting-house. There are several quarries of good 
crystalline limestone included in this lateral valley. One of these is near Hume's Grist Mill on Whiteclay 
Creek, and two others are at William Jackson's, towards the Western end of the trough. The point of 
junction of this small valley, sometimes called Pleasant Valley, with the main basin, is in the neighbourhood of 
Joshua Pusey's MiU. The furthest Westward point at which limestone has been detected in this narrow belt is 
a little S. of West Grove Meeting-house, where a tradition of the neighbourhood alleges it was met with many 
years ago in a well, and the topography seems to testify that the rock may prolong itself thus far. Excellent 
crystalline limestone, well adapted for agricultural and other uses, is quarried at William Jackson's ; some of 
the beds being pure white carbonate of lime, while others consist more or less of dolomite. Brownish mica 
occurs in these beds, as in nearly all the limestone quarries of this class throughout the county. Adjacent to 
this quarry there occur scattered chunks of altered white Primal sandstone imbedding small crystals of Rutile. 

In the mica- slate bordering the limestone of Pleasant Valley, there have occasionally been found segregated 
nodules containing a compact Kyanite. 

Iron ore, but apparently not in large deposits, occurs S. of West Grove Meeting-house. 

A tooth of Mastodon giganteus, apparently the fifth molar, was found some years ago in Pleasant Valley, 
about one mile E. of William Jackson's, on the East Branch of Whiteclay Creek. 

(2.) The main trough of limestone throws oW another and shorter branch, diverging, like the last described, 
from the Southern side, at a point between the two branches of the East Whiteclay Creek, not far W. of 
Hicks's Grist Mill. This smaller valley rims for about one mile and a half to a point a little N. of West Grove 
Meeting-house. The limestone has, as yet, been very little opened, or quarried, in this smallest branch of the 
general basin. 

Though the limestone of this branch-basin, N. of Pleasant Valley, ranges apparently in a continuous belt, 
it has been quarried hitherto at only two points : the most Eastern one is where it was wi'ought some years ago 
by Eobert Michener ; and the more Western, at present wrought by Henry Story, is one-fourth of a nule N. of 
West Grove Meeting-house. 

(3.) The main or Northern fork of the basin stretching towards the Middle Branch of Whiteclay Creek 
approaches to within half a mile of Kuisey's Clover Mill. Between the East Branch of Whiteclay and the 
Western end, it contains three or four considerable quarries of the crystalline limestone. The chief of these are 
known as Bailey's and Philips's. This last-named quarry, being situated farthest to the South-west of all the lime- 
stone deposits in this part of Chester County, supplies stone and lime for agricultural uses to a circle of country 
to the S. and W., extending to twelve or even twenty miles. Though it is evident from the topographical 
features of the whole limestone trough, from the Eed Lion Inn on the E. to Philips's Quarry on the W., that 
it is a true synclinal basin, yet, from the appearance in its more centiul parts of occasional exposures of the 
upper Primal slates, and even of the subjacent gneiss rocks, it is probable that the bed of the valley is more or 
less undulating, and that the limestone is not everywhere absolutely continuous. 

Uplifts of Gneiss, and Dykes of Granite. — In fact, there seems to extend an anticlinal axis of gneiss parallel 
with the Southern margin of the trough, the whole way from Joel Bailey 's, a little West from the West Branch of 
Eedclay, to Hicks's Grist Mill on the East Branch of Whiteclay, a distance of more than three miles. Connected 
with this line of uplift we may occasionally detect an obscure outburst of granite. The gneiss is itself massive 
and granitic. The anticlinal structure of this narrow protruded belt of older rock is Avell seen on the farm of 
Joel Bailey. 

The following little sketch exhibits its features as exposed near his house. This anticlinal is said to range 



for nearly two miles to the Eastward, and to approach the East Branch of Eedclay ; but I have not traced it there. 



Fig. 30. — Broken Saddle of Gneiss in Auroral Limestone on Bailey's Farm. 




228 



INSULATED TRACTS OE LIMESTONE. 



Granite Dykes. — Just N. of Hicks's Grist JMill white granite shows itself in a low ridge, with contorted 
materials of the Primal white sandstone, borne through the limestone apj^arently by the intrusion of the 
granite. 

There is a third dyke of granite, possibly a branch of that which ranges by Hicks's Grist Mill, which passes 
S. on the South side of Baker's Quarry, between the Branch Basin containing this quarry and that at William 
Jackson's. This dyke extends from near Baker's Quarry to a point about one-fourth of a mile N. of West 
Grove Meeting-house. 

Another but shorter anticlinal uplift of granitic gneiss passes through the farm of WiUiam Jackson in 
Pleasant Valley, and appears to range for a mile or more North-eastward, passing under the knoll upon which 
the Locust Grove School-house stands. 

This protrusion of the ancient gneiss rocks in anticlinal undulations through the overlying limestone, some- 
times with traces of the Primal white sandstone and Primal micaceous crystalline slates, sometimes without any 
vestiges of them, is a feature confirming the evidence derived from various other phenomena, of the original 
unconformity in deposition of the Primal and Auroral strata upon the gneissic rocks. 

Besides the quarries already enumerated, there are two or three good ones in the vicinity of Joel Bailey's. 
In all of these artificial exposures the general character of the limestone is very similar. It is generally a 
crystalline dolomitic limestone, sometimes very granular, disposed in massive beds, and contains, for the most 
part, more or less segregated mica, talc, and other minerals, the mica being rarely absent. In consequence of 
these extraneous substances, it seldom yields, when burnt, a perfectly white lime, though in nearly aU the 
quarries some layers may be found so free from these foreign minerals as to produce, if care be observed in 
quarrying it, a stone convertible to lime of the very finest quality. 

An interesting geological feature connected with this long and shallow trough of Auroral limestone, is the 
marginal outcrop of Primal white sandstone, and Primal crystalline slate, which almost everywhere borders it. 
These rocks are best seen along the old street road, and the lanes leading out from it, upon the Northern side of 
the basin. The conformable dip of the sandstone under the edge of the limestone, or towards the centre of the 
basin, is well exhibited at the street road opposite Joel Bailey's, and again at Taggart's cross-roads farther E. 

In some of the quarries the limestone, especially near the Southern margins of the trough and its branches, is 
overlaid by micace,ous and other crystalline slates, identical almost in composition with the micaceous crystalline 
schists of the Primal series. These are evidently but the intercalated argillaceous beds which almost every- 
where belong to the lower part of the Auroial limestone formation. In truth, it would seem as if nearly all the 
limestone of this and the other small valleys of the district belonged to the very base of the formation, or that 
portion which presents a type of passage from the Primal or Schistose into the Auroral or Magnesian limestone 
series ; and this view is in consonance with the obvious shallowness of aU the limestone masses embraced within 
these troughs. 

Between the Southern border of this Street Road basin and the Northern edge of the Kennet Square limestone 
trough, or that bounded by the Toughcanem ridge, extremely little genuine gneiss shows itself at the surface, 
and that which does appear is the hornblende variety. It is obvious that the anticlinal belt wliich divides 
these two zones of Auroral limestone is here composed mainly of the older Primal slates, under the highly- 
crystalline micaceous type, which they wear so generally throughout all the Southern district of Pennsylvania. 
The true Gneissic or genuine Hypozoic metamorphic rocks, elevated only in narrow and broken fingers to the 
Westward of the Brandywine, here hardly lift themselves to the surface. The Primal white sandstone on both 
the N. and S. sides of the Street Road Limestone Basin, possesses all the features distinctive of this rock under 
its most metamorphosed form. Thus, where it dips gently Southward under the limestone on the North side of the 
valley near the Red Lion Inn, it contains the same minute broken crystals of schorl, the same thin partings of 
highly crystalline talc, and wears the same felspathic and semi-vitreous aspect which so strongly characterise it 
throughout all its outcrops bordering the great limestone valley of Montgomery and Chester counties. 

It is not practicable to make out in strictly correct sections the undulations and dips of the strata, either in 
this or any other of the more complicated of these limestone troughs ; but their structure is evidently identical 
with that of the Appalachian basins generally. The inclination of the rocks on the S. or S.E. side is either 



QUARRIES. 



229 



steep or inverted, unless where an actual dislocation forces the approximately level limestone to abut against 
uplifted walls of older gneiss or granite, while the dip on the N. or N.W. side is almost universally Southward 
at a gentle angle. 

Both in Baker's Quarry in the Middle Branch of the Street Road Basin, and at Jackson's in the Southern 
Branch, the dip of the limestone is for the most part very gentle ; that at Baker's flatly undulating, while that 
at Jackson's is at the low angle of 20° Southward into the base of the hill which bounds it. In William Jackson's 
Quarry well-developed ciystals of phosphate of lime have occasionally been found ; and the same mineral has 
been met with one mile WS.. of Chatham in a soil derived from the Primal mica-slate. Asbestos, in flexible 
sheets like paper, has also been found in Jackson's Quarry. 

Neither in this nor in any other of these local isolated tracts of Auroral limestone and Primal white sand- 
stone, do we meet with these rocks under a fossiliferous type. Obscure traces of the Scolithus, the sole fossil 
of the Primal white sandstone yet discovered in Pennsylvania, have been once or twice met with iipon loose 
fragments of the rock ; but this is the only instance of organic remains yet discovered. But this absence of 
fossUs from these the most ancient of all the Palaeozoic deposits of our country, need not at all surprise us, since 
their occurrence is extremely rare even in those basins of the same formations farther N., where the strata are 
much less altered and crystalline. Indeed, we know of no discovery of organic remains in the lowest beds of 
the Auroral limestone equivalent to the rock of these valleys in any part of the middle States. 

Nearly in a hue prolonged Eastward from the Street Road Basin, but some three and a half miles Eastward 
from its Eastern termination at the Red Lion Inn, there is an insulated outcrop of both the Auroral limestone 
and the Primal white sandstone just W. of the Brandywine a little below Brinton's Ford. This is at Good- 
wood's Quarry (formerly Harvey's). The quarry has not been wrought for several years. The limestone is for 
the most part sandy. Sandstone is scattered on the surface in the immediate vicinity of the limestone, but 
does not exhibit itself in place. Very probably this patch of limestone is an outstanding remnant of a more 
continuous belt which may once have connected it with that of the Street Road Basin, for it seems to lie in the 
same general synclinal wave in the older strata. In like manner, there can be very little doubt that the Eastern 
prong of the Kennet Square Basin, now embracing the detached quarries of Passmore, Mendon Hall, and Nichol's, 
was once prolonged across the Brandywine at Chadd's Ford ; for we have the plainest proofs in the synclinal 
dipping of the hornblende gneiss of that Adcinity, that a great natural trough or basin, competent to contain, 
until denuded, a belt of Primal and Auroral rocks, does here exist. 

Belt Fourth. — N. of the long basin of the Street Road above described, and distant from it about two'miles, 
there lies a much smaller trough or synclinal fold in the strata, containing a more or less continuous band of 
crystalline Auroral limestone, extending for about three miles from near the Drover's Inn, W. of Unionville, to 
nearly the N. line of London Grove Township. This narrow belt, marked by a narrow irregular valley, passes 
less than half a mile to the N.W. of West Marlborough Inn. In this vicinity, and likewise nearer to the 
Drover's Inn at Logan's Quarry, the limestone has been quarried to some extent. The most western quarry of 
this tract is J. C. Bailey's, situated about one mile S. of W. from the West Marlborough Inn ; but the features 
of the country and the soil indicate that the limestone belt is prolonged considerably further South-westward in 
the direction of Cook's Grist Mill, though the rock has nowhere been opened. 

Traces of the Primal white sandstone are to be met with on the margin of this small trough. Between 
West Marlborough Inn and London Grove Post-office, and even further to the S., the older Primal rocks, here 
in the condition of true micaceous slates, occupy a broad anticlinal belt, their south-dip towards the Street Road 
Limestone Basin being obvious in all the neighbourhood around London Grove Meeting-house and Post-oflice. 
Between the Friends' Little Meeting-house and Pusey's Grist Mill, we pass over the South-east-dijiping outcrop 
of this Primal sandstone, the same which forms the Northern boundary of the Street Road Basin. 

In Eli Logan's Quarries, about one mile W. of Unionville, the limestone dips to the S.E. about 30°, but 
irregularly, and with some remarkable folds. Resting apparently upon the limestone, there is a white gneissoid 
rock, possibly only a highly-altered or crystalline form of the upper Primal slates, in alternation with the lime- 
stone. It is a conceivable supposition, however, that this rock pertains to the true gneiss formation, and that 
all the strata in this quarry are inverted. 



230 



INSULATED TRACTS OF LIMESTONE. 



In the anticlinal belt whicli separates the Street Eoacl trough of limestone from that of West Marlborough 
Inn, there would seem to be very little or no genuine gneiss W. of the Meridian of Unionville ; but between the 
Brandpvine Creek and Unionville, that rock does appear in occasional narrow uplifts. What seems to be 
genuine hornblende gneiss occurs near the Marlborough Meeting-house, some two miles E. of Unionville. The 
rock here contains some epidote. 

Belt Fifth.- — The next and most Northern principal belt of the crystalline Auroral limestone occupies a long 
and narrow trough in the strata extending from Boardley Run, one mile W. of Marshallton, to near the South- 
west corner of West Marlborough Township, a distance of about nine miles. It is not certain that we have here 
a simple continuous synclinal trough ; for though the natural exposures and the quarries of the limestone aU lie 
in one very straight and narrow line, parallel with the other basins, and with the general strike of the strata of 
the country, yet these developments are too far asunder, and the topographical features of the belt are too 
irregular, to allow us to assert positively that the limestone is strictly connected along this whol